/sci/ - Science & Math » Thread #9537723

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/sqt/ Stupid Questions Thread

Anonymous Fri 23 Feb 05:10:06 2018 No.9537723 View Reply Original Report

Quoted By: >>9538055 >>9539813 >>9540214 >>9540397 >>9540629 >>9540858 >>9541343 >>9543602 >>9544445 >>9544728 >>9546385

This thread is for questions that don't deserve their own thread.

Tips!
>give context
>describe your thought process if you're stuck
>try wolframalpha.com and stackexchange.com
>How To Ask Questions The Smart Way http://www.catb.org/~esr/faqs/smart-questions.html

Previous thread >>9527179

Anonymous

Anonymous Fri 23 Feb 2018 07:52:38 No.9538003 Report

Quoted By: >>9544603

I can't fucking wrap my head around how you find the radii in calc2 volume shit. So is it just the value from the center of the circle minus the outer function?
So between let's say an area between y = 1/x, x= 1, x = 3, and y = 0 rotated about y = -5. Would the radius just be -5 - (1/x) for the large circle and -5 for the small circle?

Anonymous

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Anonymous Fri 23 Feb 2018 08:31:08 No.9538055 Report

Quoted By: >>9538058 >>9538210 >>9539282 >>9547065

>>9537723
How do I solve question 25 and 26 I'm really confused

Anonymous

Anonymous Fri 23 Feb 2018 08:32:55 No.9538058 Report

Quoted By: >>9538062

>>9538055
What have you tried?

Anonymous

Anonymous Fri 23 Feb 2018 08:38:31 No.9538062 Report

Quoted By: >>9538063

>>9538058
I tried using factories multiplication and exponentials but I can't seem to figure out the sequence

Anonymous

Anonymous Fri 23 Feb 2018 08:39:35 No.9538063 Report

Quoted By:

>>9538062
Factorials

Anonymous

Anonymous Fri 23 Feb 2018 11:10:17 No.9538207 Report

Quoted By: >>9538213

I'm a first year maths major taking physics classes and they're so boring. When I try to give a description of what I'm studying it still sounds cool (muh "discovering and comprehending the universe") but it's just not fun. Should I drop it and take CS classes?

Anonymous

Anonymous Fri 23 Feb 2018 11:13:39 No.9538210 Report

Quoted By: >>9538448

>>9538055
sum -1^n+1 (2n)!/[2^n(n!)] / (2n-1)! = -1^n+1 * 2n/2^n(n!) = -1^n+1 /(n-1)!/2^n-1
https://www.wolframalpha.com/input/?i=sum+(-1)%5E(n-1)+%2F(n-1)!%2F2%5E(n-1)
= .606...

Anonymous

Anonymous Fri 23 Feb 2018 11:14:44 No.9538213 Report

Quoted By:

>>9538207
>Should I drop it and take CS classes

Fuck no, learn that shit by yourself.

Anonymous

Anonymous Fri 23 Feb 2018 11:24:05 No.9538220 Report

Quoted By: >>9538425

How do I into anatomy?

Would like to learn how the body works/functions but don't know where to start.

Obviously I have a good foundation of knowledge and have previously done biology so I'm not a complete beginner.

Anonymous

Anonymous Fri 23 Feb 2018 13:17:17 No.9538325 Report

Quoted By: >>9538542

Whats the physical measure of mass floating within a star system beyond the star itself called? Do astronomers index that or is it too early to estimate?

What are some good stars in our neighborhood to turn into matryoshka brains?

Anonymous

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Anonymous Fri 23 Feb 2018 14:02:08 No.9538398 Report

Quoted By: >>9538410 >>9538424

What are some good books to learn electronics?

Anonymous

Anonymous Fri 23 Feb 2018 14:06:42 No.9538410 Report

Quoted By: >>9538433

>>9538398
There aren't any. To learn electronics you have to do electronics projects.

Anonymous

Anonymous Fri 23 Feb 2018 14:15:12 No.9538424 Report

Quoted By: >>9538433

>>9538398
http://4chan-science.wikia.com/wiki/Electrical_and_Electronics_Engineering#Circuit_Analysis
http://4chan-science.wikia.com/wiki/Electrical_and_Electronics_Engineering#Electronics
http://4chan-science.wikia.com/wiki/Electrical_and_Electronics_Engineering#Bible
http://4chan-science.wikia.com/wiki/Electrical_and_Electronics_Engineering#Analog_Electronics

Anonymous

Anonymous Fri 23 Feb 2018 14:16:14 No.9538425 Report

Quoted By:

>>9538220
http://4chan-science.wikia.com/wiki/Biology_Textbook_Recommendations#Physiology

Anonymous

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Anonymous Fri 23 Feb 2018 14:18:30 No.9538433 Report

Quoted By:

>>9538410
>>9538424
Thanks!

Anonymous

Anonymous Fri 23 Feb 2018 14:29:31 No.9538448 Report

Quoted By:

>>9538210
How did u get that answer

Anonymous

Anonymous Fri 23 Feb 2018 14:30:30 No.9538451 Report

Quoted By:

Interested in Tesla. Don't understand fuck all I'm reading. 3 6 9 explains the universe? Wut? Where do I start? And I mean Start.
Is there even any chance for a brainlet to grasp this shit?

Anonymous

Anonymous Fri 23 Feb 2018 14:32:02 No.9538455 Report

Quoted By: >>9538474 >>9538483

Explain MCMC to me like I'm retarded

Anonymous

Anonymous Fri 23 Feb 2018 14:47:36 No.9538474 Report

Quoted By: >>9538477

>>9538455
What's MCMC?

Anonymous

Anonymous Fri 23 Feb 2018 14:49:11 No.9538477 Report

Quoted By:

>>9538474
markov chain monte carlo

Anonymous

Anonymous Fri 23 Feb 2018 15:00:57 No.9538483 Report

Quoted By:

>>9538455
Construct a Markov chain whose stationary distribution is the posterior of your model given data and iterate it until the desired number of samples are obtained.

Anonymous

Anonymous Fri 23 Feb 2018 15:32:34 No.9538529 Report

Quoted By: >>9538549 >>9539598

Math retard here. Can I get an explanation why Zd = Za + Zb means d is gcd(a,b). I can follow thr proofs and see that they aren't wrong but i cannot get that intuitive understanding. Btw Z is the integers

Anonymous

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Anonymous Fri 23 Feb 2018 15:42:00 No.9538542 Report

Quoted By:

>>9538325

cmon guys

Anonymous

Anonymous Fri 23 Feb 2018 15:47:12 No.9538549 Report

Quoted By: >>9539598

>>9538529
Hint: $d\,\in\,a\,\mathbf Z\,+\,b\,\mathbf Z$

Anonymous

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Anonymous Fri 23 Feb 2018 17:06:38 No.9538674 Report

Quoted By: >>9538681 >>9538682 >>9539606

This a total brainlet question, butI'm teaching myself some basic programming in Python and I'm stuck on printing this table correctly.

Here's my the current output:
n Triangular Numbers
--- --------------
5 15.0
5 15.0
5 15.0
5 15.0
5 15.0
Here's what I'm trying to do:

n Triangular Numbers
--- --------------
1 1
2 3
3 6
4 10
5 15

Can anyone help me out here?
Pic related

Anonymous

Anonymous Fri 23 Feb 2018 17:10:14 No.9538681 Report

Quoted By: >>9539262

>>9538674
i is the variable that changes during each iteration of the loop, not n

Anonymous

Anonymous Fri 23 Feb 2018 17:10:23 No.9538682 Report

Quoted By: >>9539262

>>9538674
you never use i in the loop, change
n *(n + 1) / 2 too i*(i +1) / 2

Anonymous

Anonymous Fri 23 Feb 2018 18:20:22 No.9538797 Report

Quoted By: >>9539617

Let $x,y,n$ be integers. Is it true that $n^4 + \frac{4n^3 x}{y} + \frac{6n^2 x^2}{y^2} + \frac{4nx^3}{y^3}$ is an integer if and only if $\frac{4nx^3}{y^3}$ is an integer?

Anonymous

Anonymous Fri 23 Feb 2018 19:23:16 No.9538913 Report

Quoted By: >>9539148 >>9539165

I have to find a vector which is not an element in the Span{V1,V2} where V1 and V2 are:
$\begin{bmatrix}1\\1\end{bmatrix}\begin{bmatrix}2\\-1\end{bmatrix}$

So I tried just solving this system where the last column is the right hand side of the equations:
$\begin{bmatrix}1&2&a\\1&-1&b\end{bmatrix}$
Which gives me:
$\begin{bmatrix}1&0&a-\frac{2(a-b)}{3}\\0&1&\frac{b-a}{3}\end{bmatrix}$

Since there's no row with [0...0 | b], I assume no such vector can be found?

But clearly I'm an idiot and must have done everything wrong somehow.

Anonymous

Anonymous Fri 23 Feb 2018 20:17:37 No.9539016 Report

Quoted By: >>9539182

Why is it that sometimes after I fuck a girl my cock still smells like her pussy up to a week after fucking her? I take showers and shit. Clean STD panel.

Anonymous

Anonymous Fri 23 Feb 2018 20:30:12 No.9539034 Report

Quoted By:

This is more of a career question. I did my undergrad in engineering and am currently serving in the military. In the military I've become fairly interested in pure maths and have gone through a few books on analysis (I had some brief exposure to complex analysis as an undergrad but that's it). If I wanted to pursue maths further after the military, I think I'd be locked out of any graduate prorgam since my undergraduate coursework wouldn't be sufficient background. Would it be worth it to get a second BSc level degree in maths or should I just fuck off and keep it as a hobby?

Anonymous

Anonymous Fri 23 Feb 2018 21:17:30 No.9539148 Report

Quoted By:

>>9538913
Those two vectors form a basis of R^2 so you won’t find any vector of the form [a,b], a,b in R that is not in the span.
Though I suppose you could say [a,b,c] is technically an answer

Anonymous

Anonymous Fri 23 Feb 2018 21:21:05 No.9539158 Report

Quoted By:

Why the buoyancy force on free body diagrams aren't in center of mass of the object?

Anonymous

Anonymous Fri 23 Feb 2018 21:22:15 No.9539165 Report

Quoted By:

>>9538913
any vector with more components than the rank of the matrix will do

Anonymous

Anonymous Fri 23 Feb 2018 21:27:02 No.9539182 Report

Quoted By: >>9539185

>>9539016
>Why is it that sometimes after I fuck a girl my cock still smells like her pussy up to a week after fucking her? I take showers and shit.
Do you use soap?

Anonymous

Anonymous Fri 23 Feb 2018 21:28:20 No.9539185 Report

Quoted By: >>9539190

>>9539182
Yes

Anonymous

Anonymous Fri 23 Feb 2018 21:30:01 No.9539190 Report

Quoted By: >>9539194

>>9539185
Congratulations, you are now the proud owner of an STD!

Anonymous

Anonymous Fri 23 Feb 2018 21:33:00 No.9539194 Report

Quoted By: >>9539196

>>9539190
Uhh... did you read the last part? I had a panel run and nothing came up.

Anonymous

Anonymous Fri 23 Feb 2018 21:33:54 No.9539196 Report

Quoted By: >>9539241 >>9539273

>>9539194
It can take up to 6 months for some STI's to show up on tests

Anonymous

Anonymous Fri 23 Feb 2018 21:52:32 No.9539241 Report

Quoted By:

>>9539196
So my shitty, human excuse for an olfactory system can detect things that a medical test can't?

Anonymous

Anonymous Fri 23 Feb 2018 21:59:33 No.9539262 Report

Quoted By:

>>9538681
>>9538682
Thanks!

Anonymous

Anonymous Fri 23 Feb 2018 22:06:43 No.9539273 Report

Quoted By: >>9539281

>>9539196
If your dick smells like the a plague-infected rat despite using soap, I suppose some test is gonna detect something.

Anonymous

Anonymous Fri 23 Feb 2018 22:11:48 No.9539281 Report

Quoted By: >>9539338

>>9539273
>a plague-infected rat
Does pussy really smell that bad?

Anonymous

Anonymous Fri 23 Feb 2018 22:12:00 No.9539282 Report

Quoted By:

>>9538055
For 25, write out what the factorials actually mean and cancel things out of the fraction, then notice a regularity in the remaining numbers.

Anonymous

Anonymous Fri 23 Feb 2018 22:23:32 No.9539308 Report

Quoted By: >>9539614

What is a good book on sequences and series? One that'll teach me convergence tests and theorems in general with detailed proofs (basically looking for a rigorous book on the subject)

Please, I really want to study that

Anonymous

Anonymous Fri 23 Feb 2018 22:38:22 No.9539338 Report

Quoted By:

>>9539281
It can. The only reason for suspecting STD here though is the persistence of the smell regardless of how pleasant/unpleasant it is found.

It's either that or the person in question is simply confusing smells.

Anonymous

Anonymous Sat 24 Feb 2018 00:27:34 No.9539598 Report

Quoted By: >>9539609

>>9538529
from >>9538549
Zd ? Za+Zb
Let X = (Za+Zb)?Zd
Let x be an arbitrary element of X

Since x? X ? Za+Zb, x=n*a+m*b for some n,m?Z
Therefore d|x so x = k*d for some k?Z
Hence x?Zd.
But this contradicts the construction of X
So there can be no such x
Since x was arbitrary, X must be empty
Therefore (Za+Zb)?Zd
And (Za+Zb) = Zd
QED

Anonymous

Anonymous Sat 24 Feb 2018 00:36:44 No.9539606 Report

Quoted By: >>9539613 >>9539767

>>9538674
>butI'm teaching myself some basic programming in Python

Learn C++14

>trisum = n*(n+1)/2
>15.0

You're using python 3 which made python even more autistic. In python 2, that would have been integer/integer = integer like every other language under the sun. But python 3 though that was "too confusing for the normies" so they made it integer/integer = floating point. Now you're stuck with floats even if you don't write "i*(i+1)/2.0".

Write "print(i, '\t', int(trisum))" to lob off the decimal point.

Also range(a,b) is from [a,b) so you want range(n+1)

Anonymous

Anonymous Sat 24 Feb 2018 00:38:53 No.9539609 Report

Quoted By: >>9539612

>>9539598
>Let x be an arbitrary element
>Since x was arbitrary
This is engineer level garbage writing.

Anonymous

Anonymous Sat 24 Feb 2018 00:40:15 No.9539612 Report

Quoted By: >>9539624

>>9539609
>This is engineer level garbage writing.
What's wrong with it?

Anonymous

Anonymous Sat 24 Feb 2018 00:40:25 No.9539613 Report

Quoted By:

>>9539606
>But python 3 though that was "too confusing for the normies" so they made it integer/integer = floating point.
jesus

Guido is proof that the brainlet continuum is only satisfied in a nonstandard model.

Anonymous

Anonymous Sat 24 Feb 2018 00:40:39 No.9539614 Report

Quoted By:

>>9539308
u can just wiki that anon

newton's method is for women, real men use the secant method

Anonymous

Anonymous Sat 24 Feb 2018 00:40:51 No.9539615 Report

Quoted By: >>9539616 >>9539625 >>9539630

whats the difference between electricity and magnetism? Why are magnet poles labeled north and south if they are just positive and negative charges that attract/repel kind of like a voltage causes electrical current flow? I am aware this is definitely a stupid question....

Anonymous

Anonymous Sat 24 Feb 2018 00:41:27 No.9539616 Report

Quoted By:

>>9539615
>whats the difference between electricity and magnetism?
about 90 degrees

Anonymous

Anonymous Sat 24 Feb 2018 00:42:18 No.9539617 Report

Quoted By:

>>9538797

(n+nx/y)^4

Anonymous

Anonymous Sat 24 Feb 2018 00:45:09 No.9539624 Report

Quoted By: >>9539629

>>9539612
Nobody (except engineers) writes like that. When you say "let $x \in X$ " in a proof, it's clear that you are proving something of the form $\forall x \in X : P(x)$ , so x is arbitrary.

Anonymous

Anonymous Sat 24 Feb 2018 00:45:36 No.9539625 Report

Quoted By:

>>9539615
Magnetism is just a relativistic illusion of electricity.

Anonymous

Anonymous Sat 24 Feb 2018 00:47:15 No.9539629 Report

Quoted By: >>9539638

>>9539624
>I'm using logical quantifiers!
>It's now 1000 times more rigorous!

Brainlet cs majors belong in >>>/g/

Anonymous

Anonymous Sat 24 Feb 2018 00:47:17 No.9539630 Report

Quoted By:

>>9539615
>whats the difference between electricity and magnetism?
Only one of them exists physically.

Anonymous

Anonymous Sat 24 Feb 2018 00:50:16 No.9539638 Report

Quoted By: >>9539647

>>9539629
You appear to be a brainlet C"S" major yourself if you think anyone actually writes quantifiers in papers outside of logic. You are proving a universally quantified statement though, so writing the garbage you did is redundant.
>rigorous
I said nothing about "rigor". It's simply a bad writing style.

Anonymous

Anonymous Sat 24 Feb 2018 00:57:19 No.9539647 Report

Quoted By: >>9539648

>>9539638
So basically, what he typed wasn't wrong, you just don't like it.

Anonymous

Anonymous Sat 24 Feb 2018 00:58:04 No.9539648 Report

Quoted By:

>>9539647
I didn't claim anything was wrong. You will simply be laughed at for writing that in anything serious, just giving you a heads up.

Anonymous

Anonymous Sat 24 Feb 2018 01:15:58 No.9539680 Report

Quoted By: >>9539727

Is there a definition of eigenvectors in a group theory or topology sense?

In the sense that the direction or span of the vector remains unchanged during a transformation, I'd like to think you can discuss properties of symmetry belonging to this eigenvector from a point of view of group theory and maybe topology.

Anonymous

Anonymous Sat 24 Feb 2018 01:25:10 No.9539688 Report

Quoted By:

Help /sci/ I'm getting more and more confused with this. Help me answer the following questions

What is the definition of 'a>b'? Or is it an undefined concept? (as in, it's just a total order relation on numerical sets)

Is a>a true for any a at all? If no, why?

Also, my book says that, given the maximum of a subset of R exists, it's always equal to the least upper bound. Why is it so? Is there any case where the least upper bound exists but the maximum doesn't? What the fuck

Also, if there's any source of info (books, videos, etc) that could help me understand anything related to the bounding of subsets of R, I would be very very grateful. Most calculus books skip this stuff but my course is heavy on this and I'm preparing for it.

Anonymous

Anonymous Sat 24 Feb 2018 01:31:13 No.9539703 Report

Quoted By: >>9539708 >>9539758 >>9539771

Can you please help me on this? I'm getting stuck

Why is it that, given that the maximum of a subset of R exists, it is ALWAYS equal to the least upper bound of that same subset?

And, for example, considering the set of all real numbers such that x > 4, is 4 the least upper bound? How can I prove that?

Also I'd really appreciate any source of info (books, videos, anything really) regarding the bounding of R subsets. My calculus course will be very heavy on this and most books I've looked for tend to skip this subject.

Anonymous

Anonymous Sat 24 Feb 2018 01:33:03 No.9539708 Report

Quoted By:

>>9539703
>Why is it that, given that the maximum of a subset of R exists, it is ALWAYS equal to the least upper bound of that same subset?
Look at the definition of least upper bound and then try to prove that the maximum fits this definition.

>And, for example, considering the set of all real numbers such that x > 4, is 4 the least upper bound?
No, but if you meant x<4, then yes.

Anonymous

Anonymous Sat 24 Feb 2018 01:45:29 No.9539727 Report

Quoted By: >>9539743

>>9539680
https://en.wikipedia.org/wiki/Group_action#Orbits_and_stabilizers

Anonymous

Anonymous Sat 24 Feb 2018 01:53:53 No.9539743 Report

Quoted By:

>>9539727

thanks i'll give it a read.

Anonymous

Anonymous Sat 24 Feb 2018 01:59:45 No.9539758 Report

Quoted By:

>>9539703
Let S?R and assume max(S) exits. By definition:
max(S) = x s.t. (?s?S) s?x
sup(S) = z s.t. (?r?R) r?x

If s<r, .... contradiction
If r<s, .... contradiction
Therefore r=s?

>Also I'd really appreciate any source of info (books, videos, anything really) regarding the bounding of R subsets. My calculus course will be very heavy on this and most books I've looked for tend to skip this subject.

Sounds more like you need help with proofs and mathematical reasoning. Read "A Transition to Advanced Mathematics".

Anonymous

Anonymous Sat 24 Feb 2018 02:05:00 No.9539767 Report

Quoted By: >>9539770 >>9539777

>>9539606
>Write "print(i, '\t', int(trisum))" to lob off the decimal point.

After my original post I totally realized that I neglected to write it as an int. I wasn't too concerned whether or not it was a float or an int, I was more focused on the logic. But definitely noted.

>Also range(a,b) is from [a,b) so you want range(n+1)

Just noticed and corrected that before I read this post. Thanks for pointing that out though! I've written some babby tier scripts in R and got used to the whole "not starting with 0" thing.

>Learn C++14
This is definitely a total brainlet question, but I'm not familiar with lower level languages, mainly the whole deal with compilers. Is a compiler available for free or is it something which I would need to pay for?

Sorry for the n00b question, I've only used Python and a little bit of R so anything C related is a mystery to me at the moment. I'm an economics/statistics undergrad so R and Python are the main languages used at my uni.

Anonymous

Anonymous Sat 24 Feb 2018 02:06:05 No.9539770 Report

Quoted By:

>>9539767
>After my original post I totally realized that I neglected to write it as an int.

Shit I meant float.

Anonymous

Anonymous Sat 24 Feb 2018 02:06:44 No.9539771 Report

Quoted By: >>9539788

>>9539703

Let S?R and assume max(S) exits. By definition:
max(S) = x?S s.t. (?s?S) s?x
sup(S) = z?R s.t. (?s?S) s?z & (?r?R) if (?s?S) s?r, then z?r

If x<z, .... contradiction
If z<x, .... contradiction
Therefore z=x?

>Also I'd really appreciate any source of info (books, videos, anything really) regarding the bounding of R subsets. My calculus course will be very heavy on this and most books I've looked for tend to skip this subject.

Sounds more like you need help with proofs and mathematical reasoning. Read "A Transition to Advanced Mathematics".

Anonymous

Anonymous Sat 24 Feb 2018 02:09:30 No.9539777 Report

Quoted By: >>9539779

>>9539767
>This is definitely a total brainlet question, but I'm not familiar with lower level languages, mainly the whole deal with compilers. Is a compiler available for free or is it something which I would need to pay for?

https://www.visualstudio.com/downloads/
https://clang.llvm.org/

Anonymous

Anonymous Sat 24 Feb 2018 02:10:09 No.9539779 Report

Quoted By:

>>9539777
>https://www.visualstudio.com/downloads/
Well fuck me. Thanks for the links!

Anonymous

Anonymous Sat 24 Feb 2018 02:18:35 No.9539788 Report

Quoted By: >>9539792

>>9539771
I've studied a lot of proofs, that's not really the problem. I couldn't get good maximum and supreme definitions to work with though. That's a really good book your recced me, it helped me a lot.

Anonymous

Anonymous Sat 24 Feb 2018 02:21:10 No.9539792 Report

Quoted By:

>>9539788
helped me a lot in the past, that's what I tried to mean lol,

Anonymous

Anonymous Sat 24 Feb 2018 02:38:54 No.9539813 Report

Quoted By: >>9539817

>>9537723
the last version of this was too trivial

you were very kind to answer without being patronising

how many gets should a thread with n replies have for it to have a significantly low number of gets

Anonymous

Anonymous Sat 24 Feb 2018 02:41:45 No.9539817 Report

Quoted By:

>>9539813
You can get this dick n your ass

Anonymous

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Anonymous Sat 24 Feb 2018 02:52:36 No.9539827 Report

Quoted By: >>9539835 >>9539853 >>9539854

(Alpha must be an integer btw)

So the integral is equal to 1,234,567! - 999,999!

I have to find a number to subtract from (1,234,567! - 999,999!) to make it a perfect square.

Anyone have any ideas?

Anonymous

Anonymous Sat 24 Feb 2018 02:59:33 No.9539835 Report

Quoted By: >>9539844

>>9539827
You can literally calculate $\int_0^\infty x^n\,\mathrm e^{-x}\,\mathrm dx$ by induction and integration by parts.

Anonymous

Anonymous Sat 24 Feb 2018 03:04:02 No.9539844 Report

Quoted By:

>>9539835
Yes, I know...
the integral is equal to 1,234,567! - 999,999!

But those are really big numbers.

The problem I am having is finding an integer to subtract from the integral to make it a perfect square.

Anonymous

Anonymous Sat 24 Feb 2018 03:14:49 No.9539853 Report

Quoted By:

>>9539827
Never mind, I may have figured it out

Anonymous

Anonymous Sat 24 Feb 2018 03:15:04 No.9539854 Report

Quoted By:

>>9539827
s=round(sqrt(1234567!-999999!))
-alpha = s^2-1234567!+999999!

Anonymous

Anonymous Sat 24 Feb 2018 04:29:43 No.9540025 Report

Quoted By: >>9540241

I studied Biomedical Engineering with a focus in computational modeling and we ALWAYS used Matlab in both undergrad and grad at 2 different schools. Yet none of the job postings I look at want Matlab. Should I learn another language? R and Python seem to be requested frequently

Anonymous

Anonymous Sat 24 Feb 2018 05:10:59 No.9540103 Report

Quoted By: >>9540123 >>9540173

can anyone shed some light on this
>>>/tv/95071920

Anonymous

Anonymous Sat 24 Feb 2018 05:21:04 No.9540123 Report

Quoted By: >>9540150

>>9540103
There's no such thing as 'real contact', if by contact we mean our human perception of touch. Energies perturbing fields is all there are.

"When you press on something... it's not the atoms touching each other". Even if atoms were 'touching each other', considering that subatomic particles are composed of quarks, it would still be just energies perturbing each other.

Anonymous

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Anonymous Sat 24 Feb 2018 05:30:56 No.9540147 Report

Quoted By: >>9540149 >>9540248 >>9540266

I'm self-studying Basic Mathematics by Serge Lang. His exercises are straightforward for the most part, but any questions involving proofs are completely lost on me and I end up referring to the back of the book.

Are there any good guides to constructing algebraic proofs on a basic level?

Anonymous

Anonymous Sat 24 Feb 2018 05:32:12 No.9540149 Report

Quoted By: >>9540154

>>9540147
Lang is a meme.

Anonymous

Anonymous Sat 24 Feb 2018 05:33:17 No.9540150 Report

Quoted By:

>>9540123
so what you're really saying also is that the concept of things physically existing is misled? everything is just energy?

Anonymous

Anonymous Sat 24 Feb 2018 05:35:11 No.9540154 Report

Quoted By: >>9541412

>>9540149
Ah really? How so? Are there any better I should start out with?

Anonymous

Anonymous Sat 24 Feb 2018 05:46:37 No.9540173 Report

Quoted By:

>>9540103
zeno's paradox at the atomic level

Anonymous

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Anonymous Sat 24 Feb 2018 06:20:37 No.9540214 Report

Quoted By: >>9540246

>>9537723
I gave in and installed Matlab to do some problems for my modern physics course, anything I should know off the bat? I'm just using it right now for some integrals that are a pain in the ass

Anonymous

Anonymous Sat 24 Feb 2018 06:46:19 No.9540241 Report

Quoted By:

>>9540025
Python. If you know Matlab it will be a pretty quick learn.

Employed BME w/ more than a Bachelors

Anonymous

Anonymous Sat 24 Feb 2018 06:51:16 No.9540246 Report

Quoted By:

>>9540214
Skim a book to get an idea of what functions are available and how to do stuff:
http://4chan-science.wikia.com/wiki/Programming_Textbook_Recommendations#Matlab

Always google first to see if there's a built in method that can do what you want or a subpart of it

Vectorize your code whenever possible. E.g. don't write:
>for i=1:length(A)
>>if(A(i)<0)
>>>A(i)=0;
>>end %if
>end %for
But write
>A(A<0)=0;

Anonymous

Anonymous Sat 24 Feb 2018 06:52:50 No.9540248 Report

Quoted By:

>>9540147
Read Book of Proof (https://www.people.vcu.edu/~rhammack/BookOfProof/)

Give an example question of what you're struggling on.

Anonymous

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Anonymous Sat 24 Feb 2018 07:06:37 No.9540266 Report

Quoted By: >>9540278

>>9540147
Proofs are hard and not really that important if you simply want to understand and solve problems, some people here actually have classes on nothing but proving Theorems. But if you are motivated to prove them, the right way to go is to cover the whole subject and then try to attack the proofs once you get the WHOLE idea.

Anonymous

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Anonymous Sat 24 Feb 2018 07:13:35 No.9540278 Report

Quoted By: >>9540280

>>9540266
This is """fine""" only for engineers and their ilk, and the book isn't titled "Basic Engineering".

Anonymous

Anonymous Sat 24 Feb 2018 07:15:03 No.9540280 Report

Quoted By:

>>9540278
>engineers
>engineers
>engineers

Did your engineer roommate rape your ass in your sleep or something?

Maths/Calculus II

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Maths/Calculus II Sat 24 Feb 2018 07:46:58 No.9540326 Report

Quoted By: >>9540328 >>9540433 >>9540455

So I had pic related, the question was what is the value of integral from 1/2 to 3 of f(x)dx.
I tried to change bounds but it lead no where, so I simply replace the bounds of 1/2 and 3 bc I ran out of ideas, to get this answer : 1/2-(1/2)/3^2.
whats the real answer here, thanks.

Anonymous

Anonymous Sat 24 Feb 2018 07:49:16 No.9540328 Report

Quoted By: >>9540350

>>9540326
integral from 1/2 to 3 =
integral from 1/2 to 1 + integral from 1 to 3 =
-(integral from 1 to 1/2) + integral from 1 to 3

Anonymous

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Anonymous Sat 24 Feb 2018 08:10:57 No.9540350 Report

Quoted By:

>>9540328
ah I see it, Im an idiot but then why state 1-1/b^2 though?
The answer could have very well been given without that info. It seems to hold true even if the -a- bound is lower than 1.
Or is it bc I have to replace the bounds in here 1-1/b^2 for the two integrals in your answer?

Anonymous

Anonymous Sat 24 Feb 2018 08:32:45 No.9540379 Report

Quoted By: >>9540715

This is a serious question. How do I stop getting angry at people I perceive as brainlets? I don't really care about being right and wrong, I just want to not get angry at them.

Anonymous

Anonymous Sat 24 Feb 2018 08:43:59 No.9540397 Report

Quoted By: >>9541385

>>9537723
are complex numbers basically just another way of expressing the y axis?

Anonymous

Anonymous Sat 24 Feb 2018 08:54:02 No.9540413 Report

Quoted By:

How miscible is your average vegetable oil (lets say fco/mct) going to be with 200 proof alcohol? would it be possible to get a 1:1 solution that stays dissolved?

Anonymous

View Same Google iqdb SauceNAO 21767810_1676876912331613_795113 (...).png, 1MiB, 750x750

Anonymous Sat 24 Feb 2018 09:10:24 No.9540433 Report

Quoted By: >>9540725

>>9540326
35/9

Anonymous

Anonymous Sat 24 Feb 2018 09:22:08 No.9540455 Report

Quoted By: >>9540725

>>9540326
>1/2-(1/2)/3^2.
>(1/2)/3
brainlet

obviously f(x) = 3/x^3

Anonymous

Anonymous Sat 24 Feb 2018 11:35:39 No.9540629 Report

Quoted By:

>>9537723
Can someone explain the general idea of cohomology to me? The more dumbed down the better.

Anonymous

Anonymous Sat 24 Feb 2018 13:24:26 No.9540715 Report

Quoted By:

>>9540379
think about it in a logical way, first why would you get mad at someone for learning? total nonsense. Second, what do you care, you shouldnt. There are things to get mad about but you have to choose which ones are worth getting mad.

Anonymous

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Anonymous Sat 24 Feb 2018 13:31:33 No.9540725 Report

Quoted By: >>9540750

>>9540433
ok got the same answer and it makes sense.
>>9540455
nice asspull, but it doesnt seem to be right.

Anonymous

Anonymous Sat 24 Feb 2018 13:56:08 No.9540750 Report

Quoted By: >>9540765

>>9540725
https://en.wikipedia.org/wiki/Fundamental_theorem_of_calculus#Formal_statements

Anonymous

Anonymous Sat 24 Feb 2018 14:14:12 No.9540765 Report

Quoted By:

>>9540750
>3

blind lion

Anonymous

Anonymous Sat 24 Feb 2018 15:02:15 No.9540858 Report

Quoted By: >>9540865

>>9537723

how does one prove the cauchy-goursat theorem without assuming continuous f'?

it follows right from greene's theorem and the cauchy-riemann equations if you can assume f' is continuous. the material i'm reading is more of a teaching guide and provides no proofs, but most of the theorems were easy enough except this one. the subsequent proofs and theorems use the cauchy-goursat theorem while only assuming holomorphic f, which is rather unsatisfying since the book only leads the reader to prove it using greene's theorem. i realize holomorphic f implies f' continuous, but the book hasn't covered that yet and i'd like to avoid any circular logic.

Anonymous

Anonymous Sat 24 Feb 2018 15:05:02 No.9540865 Report

Quoted By:

>>9540858

my question is pretty much this one

https://math.stackexchange.com/questions/684163/continuity-of-the-derivative

except that the solutions on stackexchange use concepts outside the book i'm reading.

Anonymous

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Anonymous Sat 24 Feb 2018 17:17:34 No.9541129 Report

Quoted By:

Brainlet here, all tensors have the same mathematics? mathematically has any relationship between the stress tensor and curvature tensor?

Anonymous

Anonymous Sat 24 Feb 2018 17:41:20 No.9541184 Report

Quoted By:

Is there any area of physics that deals with algorithm or combinatoric type stuff? I have a real knack for it but dont want to go into math or cs research. Id much rather do science so I at least have a chance to make it in industry if I dont make it in academia

Anonymous

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Anonymous Sat 24 Feb 2018 18:40:03 No.9541343 Report

Quoted By: >>9541388 >>9541411 >>9541443

>>9537723
How do I go about this?

Anonymous

Anonymous Sat 24 Feb 2018 19:04:25 No.9541385 Report

Quoted By:

>>9540397
>are complex numbers basically just another way of expressing the y axis?
no
>are imaginary numbers basically just another way of expressing the y axis?
yes
as a matter of fact, one way to understand the imaginary unit is the number such that if you multiply a number on the real line by it (consider 5 for instance) then it's rotated 90 degrees on the plane (it becomes 5i). Multiply again and you've made a 180° rotation (-5).

Anonymous

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Anonymous Sat 24 Feb 2018 19:05:36 No.9541388 Report

Quoted By:

>>9541343
state what youve tried so far newfag

Anonymous

Anonymous Sat 24 Feb 2018 19:15:39 No.9541411 Report

Quoted By:

>>9541343
Assuming this is chem 1 or something, you have to incorporate the ideal gas law.

Anonymous

Anonymous Sat 24 Feb 2018 19:15:54 No.9541412 Report

Quoted By:

>>9540154
Not that anon, but yeah, Lang is a meme. Read this fac.ksu.edu.sa/sites/default/files/131_book_transition_to_advanced_mathematics.pdf

t. experienced in self-study

Daniel Velleman's How to Prove it, Solow's how to read and do proofs and Hammock's are all good books on the subject. Specially Velleman's.

Anonymous

Anonymous Sat 24 Feb 2018 19:25:16 No.9541426 Report

Quoted By: >>9541442 >>9541469

Let V be a vector space. Is this true?

$v + w \in V \implies v, w \in V [\math]$

Anonymous

Anonymous Sat 24 Feb 2018 19:31:11 No.9541442 Report

Quoted By: >>9541464

>>9541426
No. Imagine the vector space (0, y) for all y. (1, 1) + (-1, 1) = (0, 2), but neither of them are in your vector space.

Anonymous

Anonymous Sat 24 Feb 2018 19:31:11 No.9541443 Report

Quoted By:

>>9541343
a is trivial and you should be able to do it yourself.
b is trivial and you should be able to do it yourself.
c is trivial and you should be able to do it yourself.

Anonymous

Anonymous Sat 24 Feb 2018 19:42:13 No.9541464 Report

Quoted By:

>>9541442
thx

Anonymous

Anonymous Sat 24 Feb 2018 19:45:19 No.9541469 Report

Quoted By:

>>9541426
Consider the 0 vector space. The equation $x + y = 0$ has, in most vector spaces, many solutions. Not just the typical $0 + 0 = 0$

Anonymous

Anonymous Sat 24 Feb 2018 23:10:39 No.9541952 Report

Quoted By:

I'm given the transition probability matrix for a discrete Markov chain and am being asked to find the stationary distribution and the steady-state distribution (these are asked seperately). What is the difference between the two? My professor's notes never even mention steady-state distribution

Anonymous

Anonymous Sat 24 Feb 2018 23:21:03 No.9541974 Report

Quoted By: >>9541984 >>9542101

Is there any reason for LU factorization over just rref a matrix?

Anonymous

Anonymous Sat 24 Feb 2018 23:23:46 No.9541984 Report

Quoted By: >>9541993 >>9542009

>>9541974
In a computational environment LU factorization is much faster than standard Gaussian elimination. If you're just doing maths by hand there's no reason to do LU but for any serious calculations you won't want to do Gaussian elimination

Anonymous

Anonymous Sat 24 Feb 2018 23:26:21 No.9541993 Report

Quoted By:

>>9541984
LU factorization basically is Gaussian elimination you dummy, it just does it way faster. rref in MATLAB at least actually does all the individual pivots and whatnot and takes fucking ages

Anonymous

Anonymous Sat 24 Feb 2018 23:30:39 No.9542009 Report

Quoted By: >>9542057

>>9541984
I guess there must be something else I'm not getting to this, because in order to get L and U you gotta do like half of the matrix row reductions anyway, so it doesn't seem like it would actually be faster.

Anonymous

Anonymous Sat 24 Feb 2018 23:41:49 No.9542036 Report

Quoted By: >>9542097 >>9542369 >>9543488

Can someone please post a physics flowchart?

I've done some classical mechanics but don't really know where to go now. It's not as straightforward as maths (which is usually something like precalc, calc, analysis)

Alternatively a resource that outlines the proper path would be nice

Anonymous

Anonymous Sat 24 Feb 2018 23:56:13 No.9542057 Report

Quoted By: >>9542100

>>9542009
If you want to do it by hand you have to do a lot of the reductions but there are algorithmic ways of doing it that are a lot faster
https://en.wikipedia.org/wiki/LU_decomposition#Algorithms
note that the closed formula method isn't used in practice, even though it's the easiest way of understanding it on paper

Anonymous

Anonymous Sun 25 Feb 2018 00:17:52 No.9542097 Report

Quoted By: >>9542102

>>9542036
>precalc calc analysis

Linear algebra, proofwriting, differential equations, discrete math, probability and statistics, group theory, field theory, number theory, operations research, mathematical physics, set theory, geometry, algebraic geometry, differential geometry, point-set topology, algebraic topology, complex analysis, functional analysis, operator theory, commutative algebra etc. can all go pretty much anywhere between those 3

Anonymous

Anonymous Sun 25 Feb 2018 00:21:04 No.9542100 Report

Quoted By: >>9542115

>>9542057
I'm not noticing any other algorithms in the textbook, so I guess we're not gonna be doing too much computation with them then. Guess I'll familiarize myself with them on my own time.
Thanks.

Anonymous

Anonymous Sun 25 Feb 2018 00:21:24 No.9542101 Report

Quoted By: >>9542108

>>9541974
Seeking solutions to Ax = b given A, b, factorize A = LU, then Ax = (LU)x = L(Ux) = b. But figuring out what Ux is is very easy, since we can simply back-substitute. Then we can repeat the process for L(Ux) by forward substitution, and we've found x. This is a very elementary example but the idea is that certain problems benefit from certain representations of matrices.

Anonymous

Anonymous Sun 25 Feb 2018 00:21:28 No.9542102 Report

Quoted By: >>9542105

>>9542097
not effectively, retard. you should not do complex analysis without knowing precalc, among other blatantly retarded progressions you just advocated for

I understand the sentiment but it's completely irrelevant to my question

Anonymous

Anonymous Sun 25 Feb 2018 00:23:02 No.9542105 Report

Quoted By: >>9542140

>>9542102
You can't be serious.

Anonymous

Anonymous Sun 25 Feb 2018 00:24:21 No.9542108 Report

Quoted By:

>>9542101
I don't think that was the point of their question since solving Ax=b with rref(A) is also extremely fast. the question was why use LU over rref and it's due to the fact that LU is faster to compute than full on row reducing A

Anonymous

Anonymous Sun 25 Feb 2018 00:25:56 No.9542112 Report

Quoted By: >>9542435

Is it accurate to say that a gradient field is the same thing as a direction field, but just in more than 1 dimension?

Anonymous

Anonymous Sun 25 Feb 2018 00:27:36 No.9542115 Report

Quoted By: >>9542117

>>9542100
what textbook are you using out of curiosity?

Anonymous

Anonymous Sun 25 Feb 2018 00:30:24 No.9542117 Report

Quoted By: >>9542141

>>9542115
nevermind, just realized the numerical linear algebra textbook my advisor wrote doesn't even cover LU factorization

Anonymous

Anonymous Sun 25 Feb 2018 00:44:51 No.9542140 Report

Quoted By:

>>9542105
other than regretting my oversight on the word "between", I'm completely serious and just want my goddamn physics meme chart

you're irredeemably retarded if you think certain arrangements of topics aren't more sensible and productive than others

Anonymous

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Anonymous Sun 25 Feb 2018 00:44:58 No.9542141 Report

Quoted By:

>>9542117
>numerical linear algebra textbook
>no discussion of LU factorization

Anonymous

Anonymous Sun 25 Feb 2018 01:48:17 No.9542293 Report

Quoted By: >>9542303

interested in pure math.

been reading euclid's elements on my own, intend to read archimedes, apollonius and nicomachus (got a thing for the greeks). Where do I go from there? is there a some kind of reasonable order of topics to study? should I just go pre-calculus? also I like a lot the thing the greeks had (philosophy vs math vs nature vs everything) so if there are other works like this I'd love to read

Anonymous

Anonymous Sun 25 Feb 2018 01:51:29 No.9542303 Report

Quoted By:

>>9542293
Pure math means doing abstract shit without caring about real world applications. It doesn't mean outdated stuff.

Anonymous

Anonymous Sun 25 Feb 2018 02:24:06 No.9542369 Report

Quoted By:

>>9542036
For undergraduate, you're taught four major sections of physics: thermo, quantum, mechanics, and electrodynamics. Thermodynamics fits nicely after mechanics. And then after you could look into electrodynamics and follow with quantum mechanics. Relativity should probably be the last thing you look into, simply because it's the hardest topic in physics. They don't even bother trying to teach anything beyond special relativity in undergrad.

Anonymous

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Anonymous Sun 25 Feb 2018 02:54:52 No.9542415 Report

Quoted By:

How do I do analysis in Coq?

Anonymous

Anonymous Sun 25 Feb 2018 02:59:43 No.9542420 Report

Quoted By: >>9542426 >>9542431

is there more to being an A+ student(high honors, dean's list and so on) than just getting good grades? do i have to kiss a ton of ass? do i have to participate in extracurricular activities? because as of now i have an A+ in every class, but i still feel like i won't make it on the dean's list or qualify for academic scholarships which i desperately need to go to grad school

Anonymous

Anonymous Sun 25 Feb 2018 03:03:59 No.9542426 Report

Quoted By: >>9542431

>>9542420
to amend: i'm a staunch conservative and i'm not afraid to voice my opinions when appropriate. should i shut the fuck up? i don't want to end up on the shit list(if it's not already too late)

Anonymous

Anonymous Sun 25 Feb 2018 03:05:57 No.9542431 Report

Quoted By: >>9542437

>>9542420
>>9542426
>A+
>claims to know what his grade would be in the middle of the quarter
>throws in political beliefs when it's completely irrelevant

you're either going to a shitty school or living some weird head delusion

Anonymous

Anonymous Sun 25 Feb 2018 03:10:25 No.9542435 Report

Quoted By:

>>9542112
re roll for answer pls

Anonymous

Anonymous Sun 25 Feb 2018 03:10:36 No.9542437 Report

Quoted By: >>9542438

>>9542431
i've already blown through the course work for both of my engineering classes and lab. i could almost teach. i'm fucking bored

Anonymous

Anonymous Sun 25 Feb 2018 03:13:07 No.9542438 Report

Quoted By: >>9542441

>>9542437
then you go to a shitty fucking school and have no chance at going to a good graduate school. get involved in research

Anonymous

Anonymous Sun 25 Feb 2018 03:13:28 No.9542441 Report

Quoted By: >>9542444

>>9542438
you're a fucking retard

Anonymous

Anonymous Sun 25 Feb 2018 03:15:11 No.9542444 Report

Quoted By: >>9542587

>>9542441
Just saying mate the fact that your school even gives "A+"s and that you could even know what your grade is during the quarter (i.e. no curving) indicates to me that you go to a useless small state school and have no chance of accomplishing anything

Anonymous

Anonymous Sun 25 Feb 2018 04:10:01 No.9542519 Report

Quoted By:

Any rad techs here? I've noticed that the pay is kind of shit but it might be possible make up for it with call work and further specialization. Is this true? Could I end up making more than an MD if I got into on-call ED MRI shit? How are the workplace politics? Clear power divide between nurses, radiologists etc. or is it not really noticed?

Anonymous

Anonymous Sun 25 Feb 2018 04:21:49 No.9542534 Report

Quoted By: >>9542614

How do I replace functions/operations on a ti 84

Like if I do cos(5) it wouldn't be cos() it would be whatever custom thing I have in prgm

Anonymous

Anonymous Sun 25 Feb 2018 04:52:32 No.9542587 Report

Quoted By: >>9544366

>>9542444
I'm pretty sure that guy's a LARPer anyways, just ignore him.

Anonymous

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Anonymous Sun 25 Feb 2018 05:08:07 No.9542609 Report

Quoted By: >>9542617 >>9544693

How do I, scientifically speaking, turn a straight guy gay?

Asking for a friend.

Anonymous

Anonymous Sun 25 Feb 2018 05:13:44 No.9542614 Report

Quoted By: >>9542665 >>9542671 >>9543733 >>9548384

>>9542534
https://www.intmath.com/blog/wp-content/images/2011/06/exact-values-sin-degrees.pdf

Anonymous

Anonymous Sun 25 Feb 2018 05:15:56 No.9542617 Report

Quoted By:

>>9542609
Ahh, this is a simple matter of clever chemistry and biology. You will need a high dosage of trans-platin which can be placed into the subject's food supply and consumed.

Anonymous

Anonymous Sun 25 Feb 2018 05:43:44 No.9542665 Report

Quoted By: >>9542676

>>9542614
Nigga no im asking how do I edit a function in the ti 84, including like + and - operators. I just want it to say benis when you type anything

Anonymous

Anonymous Sun 25 Feb 2018 05:50:03 No.9542671 Report

Quoted By: >>9543658 >>9543684

>>9542614
Are some real numbers actually easier to write as products of complex numbers, or are those just the grossly unsimplified results of typing shit into mathematica?

Anonymous

Anonymous Sun 25 Feb 2018 05:52:44 No.9542676 Report

Quoted By:

>>9542665
I don't think you can. What you can do, though, is make a program that immediately clears the screen, then takes input with an empty string as the prompt, then gives whatever output you want. So it looks like the normal home screen and lets you enter any calculation that can be stored as a variable. I had one that gave the correct answer plus 1.

Anonymous

Anonymous Sun 25 Feb 2018 06:30:37 No.9542745 Report

Quoted By: >>9542767 >>9542778

Negative numbers: do they exist? When you are counting, you cannot count to a negative number. When you are in debt, you don't say you have negative money, you say that you owe money.

It just mind boggles me that so many "smart" people actually fall for this common math mistake. It's not like I'm some genius who's figured out the truth, this should be easy for people to understand, and yet they don't.

I know you guys will understand what I'm saying, but I'm very afraid that many people out there will just ignore it as they've already made up their minds and will refuse to acknowledge any other possible theories about number theory.

Alas, I will need some prayer and meditation to come to terms with this reality.

Anonymous

Anonymous Sun 25 Feb 2018 06:42:32 No.9542767 Report

Quoted By:

>>9542745
Death Valley has negative elevation (relative to sea level). A vacuum has negative gauge pressure.

Anonymous

Anonymous Sun 25 Feb 2018 06:48:34 No.9542778 Report

Quoted By: >>9542822

>>9542745
>Negative numbers: do they exist?
no, but we can use pairs of naturals in such a way that we know how they would behave if they did exist

Anonymous

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Anonymous Sun 25 Feb 2018 07:00:20 No.9542797 Report

Quoted By: >>9542802 >>9542827 >>9542848

Can someone explains these to me? Particularly D2. I know you are suppose to take the square roots of the elements in D2 since it's the pre-image, but clearly you cannot take a square root of -5. So what am I missing here?

Anonymous

Anonymous Sun 25 Feb 2018 07:03:16 No.9542802 Report

Quoted By:

>>9542797
Do you know how f^(-1)(A) is defined?

Anonymous

Anonymous Sun 25 Feb 2018 07:16:01 No.9542822 Report

Quoted By:

>>9542778
>pairs
No such thing.
>naturals
They don't exist either.

Anonymous

Anonymous Sun 25 Feb 2018 07:20:59 No.9542827 Report

Quoted By: >>9542830

>>9542797
>but clearly you cannot take a square root of -5
Sure you can.

Anonymous

Anonymous Sun 25 Feb 2018 07:22:50 No.9542830 Report

Quoted By: >>9542838 >>9542870

>>9542827
>R->R
>square root of negative 5
this is "stupid questions thread" not "stupid comments thread"

Anonymous

Anonymous Sun 25 Feb 2018 07:33:04 No.9542838 Report

Quoted By: >>9542862

>>9542830
>R->R
$\mathbb{R}$ is just notation for $\mathbb{R}[x]/(x^2 + p)$ for some p clear from the context.

Anonymous

Anonymous Sun 25 Feb 2018 07:39:18 No.9542848 Report

Quoted By:

>>9542797
when f: A->B, B doesn't have to equal f(A). It can be bigger. When finding the preimage, you just throw out points that weren't hit by any a in A.

Anonymous

Anonymous Sun 25 Feb 2018 07:50:24 No.9542862 Report

Quoted By: >>9542883

>>9542838
i cant even tell anymore

Anonymous

Anonymous Sun 25 Feb 2018 07:54:37 No.9542870 Report

Quoted By:

>>9542830
Square root of -5 is usually chosen to be i*sqrt{5}.

Anonymous

Anonymous Sun 25 Feb 2018 08:03:21 No.9542883 Report

Quoted By:

>>9542862
I don't understand what you're trying to say.

Anonymous

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Anonymous Sun 25 Feb 2018 08:41:04 No.9542932 Report

Quoted By: >>9542934 >>9542941

Is the book Gödel, Escher, Bach: an Eternal Golden Braid worth reading? It is kind of a big book but that is not the problem. I don't wanna waste my time and money on something that is just overhyped by normies right now. I will definitely read it in the future but right now I am looking for something that is absolutely worth it. What do you guys say?

Anonymous

Anonymous Sun 25 Feb 2018 08:42:17 No.9542934 Report

Quoted By: >>9542979

>>9542932
>Is the book Gödel, Escher, Bach: an Eternal Golden Braid worth reading?
Why don't you read it and find out?

Anonymous

Anonymous Sun 25 Feb 2018 08:48:05 No.9542941 Report

Quoted By:

>>9542932
Yes. It has very deep implications for our minds since it uses Gödel's incompleteness and completeness theorems in a Platonic way to give an intuitive proof of very deep concepts.

Anonymous

Anonymous Sun 25 Feb 2018 09:26:38 No.9542979 Report

Quoted By:

>>9542934
I already stated that I don't have time and money to waste on a disappointing book but let me elaborate. I am looking to purchase a book that will teach me something new or perhaps has some interesting subjects to talk about. GEB seemed interesting so I thought I might give it a go but a quick search online showed that people had conflicting opinions on it. That is why I wanted to know what /sci/ thinks of it. I am on a budget and have less free time to spare due to a busy lifestyle so I wouldn't want to spend valuable time reading a book that is garbage.

Anonymous

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Anonymous Sun 25 Feb 2018 10:07:14 No.9543031 Report

Quoted By: >>9543122 >>9543143

Any help with determining this analytically? Tried splitting in partial fractions, and also tried subbing in u=m^2-s^2, but didn't get much progress with either

Anonymous

Anonymous Sun 25 Feb 2018 11:00:49 No.9543122 Report

Quoted By: >>9543596

>>9543031
Looks rather designed for contour integration. Are you asked for the principal value?

You could also find the same integral with cosine instead or sine, lacking the s in the numerator, and differentiate that result with respect to r.

Anonymous

Anonymous Sun 25 Feb 2018 11:26:04 No.9543143 Report

Quoted By: >>9543596

>>9543031
How about starting out with partial fraction decomposition

Anonymous

Anonymous Sun 25 Feb 2018 15:12:37 No.9543488 Report

Quoted By: >>9543531

>>9542036
http://4chan-science.wikia.com/wiki/Physics_Textbook_Recommendations

Anonymous

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Anonymous Sun 25 Feb 2018 15:28:57 No.9543527 Report

Quoted By: >>9543545

Ok so I'm getting cubed root of -25 for the n value for the sequence. Which is obviously wrong. What am I supposed to do?

Anonymous

Anonymous Sun 25 Feb 2018 15:29:52 No.9543531 Report

Quoted By: >>9543584

>>9543488
How did you get cubed root of -25?

Anonymous

Anonymous Sun 25 Feb 2018 15:37:21 No.9543545 Report

Quoted By: >>9543584

>>9543527
post your workings. i think your forgetting a - sign somewhere.
the $\sqrt[3]{25}$ part is right though

Anonymous

Anonymous Sun 25 Feb 2018 15:48:48 No.9543584 Report

Quoted By: >>9543585

>>9543545
>>9543531
Ok i did it again and got this. Should N be 3?

Anonymous

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Anonymous Sun 25 Feb 2018 15:49:59 No.9543585 Report

Quoted By:

>>9543584
sorry forgot to post pic

Anonymous

Anonymous Sun 25 Feb 2018 15:57:51 No.9543596 Report

Quoted By: >>9545121

>>9543122
>>9543143
Tried it again with partial fractions, and got something resembling a reasonable answer

Anonymous

Anonymous Sun 25 Feb 2018 16:00:16 No.9543602 Report

Quoted By:

>>9537723
Which books are good for teaching me the physics of blackholes

Anonymous

Anonymous Sun 25 Feb 2018 16:23:03 No.9543658 Report

Quoted By:

>>9542671
I’m pretty sure they are simpler with complex numbers, even though they all cancel out in the end.

Anonymous

Anonymous Sun 25 Feb 2018 16:37:00 No.9543684 Report

Quoted By:

>>9542671
that's as simple as they can get

Anonymous

Anonymous Sun 25 Feb 2018 16:59:21 No.9543733 Report

Quoted By: >>9543845

>>9542614
Kind of weird that 42 and 87 are so complicated. Looking at 3, it’s clear you should be able to get all multiples of 3 using a few different roots. The rest you could use 1/3 angle formulas to get.

Anonymous

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Anonymous Sun 25 Feb 2018 17:21:27 No.9543770 Report

Quoted By:

can this be simplified?

Anonymous

Anonymous Sun 25 Feb 2018 17:55:14 No.9543845 Report

Quoted By:

>>9543733
actually I'm surprised 42 is so simple given how complicated sin(7) is and 42 = 2*3*7

Anonymous

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Anonymous Sun 25 Feb 2018 20:24:35 No.9544177 Report

Quoted By: >>9544242

>Find an nth-degree polynomial function with real coefficients satisfying the given conditions:

>n=3

>2 and 4i are zeros

>f(1)= -51

Please tell me how to solve this or at least refer me to a website with an explanation. I'm not asking you to do my homework, I just don't know how to solve it. I am a brainlet.

Anonymous

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Anonymous Sun 25 Feb 2018 20:31:33 No.9544198 Report

Quoted By:

Please help anons, with this >pic-related

I understand a) and b) for how it got its "Half a Rounding Unit" but I do not understand this for c), d) and e).

How has for example d) gone from 99 to 1 divided by 2? Same for the others, does not make sense to me.

Anonymous

Anonymous Sun 25 Feb 2018 20:44:52 No.9544242 Report

Quoted By: >>9544280

>>9544177
a) complex roots of real polynomials must come in conjugate pairs
b) every third degree polynomial can be written as a monic cubic in terms of roots as $p(x) = x^3 + bx^2 + cx + d = (x-r_0) (x-r_1) (x-r_2)$

Since you have two roots, you need the third. But since one is complex, you can determine the other as its conjugate. Then just multiply out the three forms.

Since you have defined it as $p(x) = 0$ , you can see that this is just as true if we multiply both sides by some constant $c\cdot p(x) = c\cdot 0 = 0$ so even though the roots can define a polynomial uniquely they cannot define it's scale. This is where the $p(1) = -51$ comes in.

Anonymous

Anonymous Sun 25 Feb 2018 20:55:26 No.9544280 Report

Quoted By:

>>9544242
Thank you very much, anon.

Anonymous

Anonymous Sun 25 Feb 2018 21:22:40 No.9544366 Report

Quoted By:

>>9542587
Yeah the fact that he thinks his political beliefs are at all relevant makes me think he's some LARPer who reads breitbart too much

Anonymous

Anonymous Sun 25 Feb 2018 21:32:25 No.9544389 Report

Quoted By: >>9544418

>>9541797 (OP)
Not exactly a stupid question, rather a general question:
How hard would be studying physics without knowing AP-level math from HS?
I'm finishing grammar school this summer with below average grades and physics is one the easiest subjects to get into here in germany, cause so few apply for it.

Anonymous

Anonymous Sun 25 Feb 2018 21:36:14 No.9544402 Report

Quoted By:

Not exactly a stupid question, rather a general question:
How hard would be studying physics without knowing AP-level math from HS?
I'm finishing grammar school this summer with below average grades and physics is one the easiest subjects to get into here in germany, cause so few apply for it.

Anonymous

Anonymous Sun 25 Feb 2018 21:42:10 No.9544418 Report

Quoted By: >>9544447

>>9544389
if you don't have calculus, physics is a bunch of shitty memorization of "formulas" with no fucking sense

Anonymous

Anonymous Sun 25 Feb 2018 21:53:10 No.9544445 Report

Quoted By:

>>9537723
Is EE a meme? Should I go with CE or AE instead?

Anonymous

Anonymous Sun 25 Feb 2018 21:54:34 No.9544447 Report

Quoted By: >>9544448

>>9544418
I had memorise 55 formulas for an Electrical Science exams with minimal calculations.

Anonymous

Anonymous Sun 25 Feb 2018 21:55:36 No.9544448 Report

Quoted By:

>>9544447
*had to

Anonymous

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Anonymous Sun 25 Feb 2018 23:01:21 No.9544603 Report

Quoted By:

>>9538003
close, but a radius is a distance so cant be negative. drawing it will help you

Anonymous

Anonymous Sun 25 Feb 2018 23:49:27 No.9544686 Report

Quoted By: >>9544698 >>9544742 >>9545746

Not sure if this belongs on /g/ or /sci/, but probably /sci/.
I've gone through 3 years of computer science, but my degree teaches us nothing about machine learning, which seems to be a hot topic research field. So i figured i would start learning by myself.
I want to write a program that decides whether a given name is a possible German name, or not.
I understand I need 2 components: the training data (e.g. Karl, Christian, and Anna are possible German names, while James, Shinzo and Mohammad are not).
Then I need to write a bot that creates a model, probably a markov chain? based on the training data. with each letter of the alphabet being a state.
then, using some basic linear algebra, i could decide how likely it is that an input name satisfies the model or not.

Am I completely wrong with this? Or do i have the right general idea

Anonymous

Anonymous Sun 25 Feb 2018 23:54:48 No.9544693 Report

Quoted By:

>>9542609
Ecstasy tabs

Anonymous

Anonymous Sun 25 Feb 2018 23:58:54 No.9544698 Report

Quoted By:

>>9544686
Machine learning is mostly statistics. Just take a class on Bayesian networks.

Anonymous

Anonymous Mon 26 Feb 2018 00:11:22 No.9544728 Report

Quoted By:

>>9537723
test

Anonymous

View Same Google iqdb SauceNAO machine_learning.png, 28KiB, 371x439

Anonymous Mon 26 Feb 2018 00:15:52 No.9544742 Report

Quoted By: >>9544796

>>9544686

Anonymous

Anonymous Mon 26 Feb 2018 00:35:53 No.9544796 Report

Quoted By:

>>9544742
very elementary system of machine learning, but okay.

Anonymous

Anonymous Mon 26 Feb 2018 02:56:59 No.9545121 Report

Quoted By:

>>9543596
Happy to hear that

Anonymous

Anonymous Mon 26 Feb 2018 03:49:48 No.9545253 Report

Quoted By: >>9545805

I have a question about power in resonators (currently studying microwave resonators but I think it applies to them all more or less the same). If I sent in a signal to a microwave resonator that had a flat power spectrum, I'd expect at the output for the power spectrum to be attenuated at frequencies other than the resonant frequencies. What happens to that power? Is it just lost as heat?

Anonymous

Anonymous Mon 26 Feb 2018 04:24:57 No.9545290 Report

Quoted By: >>9545379

Let a_i be a sequence
Given $\sum^{n}{a_i} = S(n)$

Is there any case where the following holds? $\sum^{\infty}{a_i} = \lim_{n\to\infty}{\sum^{n}{a_i}}= S(n)$

I mean, it works for a_i = i so I want to know if it works for any other case at all

Anonymous

Anonymous Mon 26 Feb 2018 05:17:12 No.9545378 Report

Quoted By:

Trying to use change-of-variable to make my life easier, but I'm not sure if this is right:

I have the following integral:

$ y_1 \int_{x_{i-1}}^{x_{i+1}} L_1 (x) dx $
And I'm told to make the variable substitution
$ z = x - x_{i-1}, dz = dx $

For the limits of integration, would this integral just become:
$ y_1 \int_{z = 2x_{i-1}}^{z = x_{i+1} + x_{i-1}} L_1 (z = x-x_{i-1}) dx $

Anonymous

Anonymous Mon 26 Feb 2018 05:20:48 No.9545379 Report

Quoted By:

>>9545290
I'm not sure what you're asking. The sum from 0 to infinity of a_i is defined to be limit as n -> infty of the sum from 0 to n of a_i.

Anonymous

Anonymous Mon 26 Feb 2018 05:34:50 No.9545410 Report

Quoted By: >>9545417 >>9545456

Is it true that if A, B subsets of X, then X\A=B is equivalent to X\B=A?

Anonymous

Anonymous Mon 26 Feb 2018 05:40:17 No.9545417 Report

Quoted By: >>9545419

>>9545410
Yes

Anonymous

Anonymous Mon 26 Feb 2018 05:41:43 No.9545419 Report

Quoted By: >>9545434

>>9545417
How to prove it?

Anonymous

Anonymous Mon 26 Feb 2018 05:49:25 No.9545434 Report

Quoted By:

>>9545419
B = X \ A = X intersect A^c.

B^c = X^c union A

X intersect B^c = X intersect (X^c union A) = (X intersect X^c) union (X intersect A)

X\B = X intersect A = A

Anonymous

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Anonymous Mon 26 Feb 2018 05:56:08 No.9545445 Report

Quoted By: >>9545449 >>9545460

I slacked off in High School and haven't used my head in a decade, but for some reason I want to catch up with science and math.

How can I do that? I really don't know how and what to study stuff anymore..
.
Not to mention I pretty much need to start from the very basics because I really don't have any self confidence with math and science anymore. I know I am dumb and it sucks.

Anonymous

Anonymous Mon 26 Feb 2018 05:58:29 No.9545449 Report

Quoted By: >>9545455

>>9545445
How far do you want to catch up?

Anonymous

Anonymous Mon 26 Feb 2018 06:02:23 No.9545455 Report

Quoted By:

>>9545449
I would say at least the end of high school as a beginning.

Anonymous

Anonymous Mon 26 Feb 2018 06:02:47 No.9545456 Report

Quoted By:

>>9545410
given
a=a&x
b=b&x
x&!a = b

x&!b ?= a
x&!(x&!a) ?= a
x&(!x+a) ?= a
x&!x + x&a ?=a
x&a ?= a
a ?= a

Anonymous

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Anonymous Mon 26 Feb 2018 06:03:52 No.9545460 Report

Quoted By: >>9545467

>>9545445

Anonymous

Anonymous Mon 26 Feb 2018 06:06:57 No.9545467 Report

Quoted By: >>9545568

>>9545460
Thank you!

Anonymous

Anonymous Mon 26 Feb 2018 07:10:51 No.9545568 Report

Quoted By:

>>9545467
Don't get calc with analytical geo it's actually shit

Anonymous

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Anonymous Mon 26 Feb 2018 07:12:07 No.9545570 Report

Quoted By: >>9545572 >>9545634 >>9545749 >>9545755

first year maths student, I'm sure this is basic for a lot of you, however I'm stuck on understanding even the fundamentals behind it

Anonymous

Anonymous Mon 26 Feb 2018 07:13:07 No.9545572 Report

Quoted By: >>9545603 >>9545780

>>9545570
What have you tried?

Anonymous

Anonymous Mon 26 Feb 2018 07:36:54 No.9545603 Report

Quoted By: >>9545606

>>9545572
well break down 108 to its prime factors of 2^2 * 3^3 and raise 3 to each power by the respective number of times, and once it surpasses 97, start the process again with whatever is left as the remainder once you divide by 97

Anonymous

Anonymous Mon 26 Feb 2018 07:38:00 No.9545606 Report

Quoted By:

>>9545603
same guy here, is this the completely wrong method?

Anonymous

Anonymous Mon 26 Feb 2018 07:58:01 No.9545634 Report

Quoted By: >>9545710 >>9545711 >>9545780

>>9545570
if |G| = n, then g^n = 1 for all g in G
|Z/97Z*| = 96
3^108 = 3^12 = 3^8*3^4
3^1= 3
3^2= 3*3=9
3^4= 9*9=81
3^8= 81*81=6561 = 62
3^12= 62*81 = 5022 = 75

Anonymous

Anonymous Mon 26 Feb 2018 08:57:29 No.9545710 Report

Quoted By: >>9545711

>>9545634
can you break this down a little bit more, I'm convfused by what you mean when you say

"if |G| = n, then g^n = 1 for all g in G
|Z/97Z*| = 96
3^108 = 3^12"

Anonymous

Anonymous Mon 26 Feb 2018 08:58:47 No.9545711 Report

Quoted By:

>>9545634
>>9545710
but thanks for the answer, much apreciated

Anonymous

Anonymous Mon 26 Feb 2018 09:57:38 No.9545746 Report

Quoted By:

>>9544686
Machine Learning in general is not about bots, and you don't need a bot for this task. Using a markov chain could work, but it's probably not going to give you good results (probably halfway between "random guessing" and state-of-the-art accuracy, so 70+% with 2 languages). If you want to get decent results, I would suggest you to use a neural network with LSTM nodes - it's AFAIK the standard whenever language is involved, but that might be too complicated for a beginner

Implementing anything in machine learning is probably a very bad idea, there are packages for everything. You usually only have to import a package and feed your training data into it.

If you really want to implement something (for learning purposes), I would suggest first using an existing package, then copying the interface of the package and trying to copy the functionality, otherwise you won't get far

Anonymous

Anonymous Mon 26 Feb 2018 10:03:57 No.9545749 Report

Quoted By: >>9545755 >>9545780

>>9545570
Why are the numbers in brackets? The usual approach for 3a would be the (modular) exponentiation by squaring, for 3b the extended euclidian algorithm can be used

Anonymous

Anonymous Mon 26 Feb 2018 10:09:56 No.9545755 Report

Quoted By:

>>9545570
>>9545749
Oh, and Fermats little theorem works too for 3b (applying it also involves modular exponentiation by squaring, so you probably used it in class)

Anonymous

Anonymous Mon 26 Feb 2018 10:35:00 No.9545780 Report

Quoted By: >>9545792

>>9545572
Good question by a math student
>>9545634
Can't even use Latex, no math student
>>9545749
>Why are the numbers in brackets?
middle schooler, don't even reply to this

Anonymous

Anonymous Mon 26 Feb 2018 10:45:00 No.9545792 Report

Quoted By: >>9545799

>>9545780
Fuck off autist. Nobody care about your metaposting.

Anonymous

Anonymous Mon 26 Feb 2018 10:49:15 No.9545799 Report

Quoted By: >>9545802

>>9545792
How is it metaposting? The one guy didn't use Latex. It makes it tedious as fuck to read what he wrote

Anonymous

Anonymous Mon 26 Feb 2018 10:50:43 No.9545800 Report

Quoted By: >>9545804

What is the purpose of infinity? It is a stupid concept which could for all real world applications be substituted for 1 000 000 000.

Anonymous

Anonymous Mon 26 Feb 2018 10:54:21 No.9545802 Report

Quoted By:

>>9545799
It's simple multiplication. You don't need latex.

Anonymous

Anonymous Mon 26 Feb 2018 10:55:06 No.9545804 Report

Quoted By: >>9545822

>>9545800
There are more people than 1,000,000,000 so therefore that number isn't high enough

Anonymous

Anonymous Mon 26 Feb 2018 10:55:18 No.9545805 Report

Quoted By: >>9546506

>>9545253
Yes. Losses in a resonator are a combination of the non-zero resistance of the cavity walls and dielectric losses (power consumed by continually changing the polarisation of the dielectric). Both of these result in power being converted to heat.

A resonator made from a perfect conductor filled with a vacuum would have no losses at any frequency. At resonance, the electric field at the cavity surface has no tangential component so there's no current and no resistive losses regardless of the actual resistance. So resonators made from imperfect conductors have resistive losses at non-resonant frequencies.

Anonymous

Anonymous Mon 26 Feb 2018 11:18:36 No.9545822 Report

Quoted By:

>>9545804
100 000 000 000

Anonymous

Anonymous Mon 26 Feb 2018 15:48:39 No.9546102 Report

Quoted By: >>9546104 >>9546335

Why is hearing considered different from touch? It's just moving air particles touching our ears

Anonymous

Anonymous Mon 26 Feb 2018 15:49:59 No.9546104 Report

Quoted By: >>9546107

>>9546102
no it's not

Anonymous

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Anonymous Mon 26 Feb 2018 15:55:08 No.9546107 Report

Quoted By:

>>9546104
how?

Anonymous

Anonymous Mon 26 Feb 2018 17:03:10 No.9546187 Report

Quoted By: >>9546203

How can you verify that a parametrisation is correct?
As a basic example, say you want to parametrise the unit circle $x^2+y^2=1$ . Obviously one parametrisation is $r(t)=(\cos t,\sin t)\,,\quad t\in[0,2\pi]$

It's easy to verify the (sin,cos) part since $\sin (t)^2+\cos (t)^2=1$ , but then how do you verify the "limits" are correct?

Anonymous

Anonymous Mon 26 Feb 2018 17:09:37 No.9546203 Report

Quoted By: >>9546327

>>9546187
You can prove that the two sets of points are the same.

If you have an (x, y) such that x^2 + y^2 = 1, prove that there is a t in [0, 2pi] such that cos t = x and sin t = y.

If you have a t in [0, 2pi], prove that (cos t)^2 + (sin t)^2 = 1.

If you have proven both, you know that the two sets of points are equivalent, which is what you want.

Anonymous

Anonymous Mon 26 Feb 2018 17:52:26 No.9546307 Report

Quoted By: >>9546626

I'm working on a homework and there's one problem I can't solve

a_n is the amount of series of length n consisting of elements of {0, 1, 2} such that a 1 on the jth place is never followed by a 1 or 2 on the j+1th place.
I need to prove that a_1=3, a_2=7, and for n >= 3, a_n=2a_{n-1}+a_{n-2}
a_1 is simple, because the series of length 1 are just 0, 1, and 2
a_2 is simple too; 00, 01, 02, 10, 20, 21, 22

But I can't figure out how to prove that for n>=3. I kind of see how it makes sense logically and I've been trying proofs by induction but I don't really see how to start

Anonymous

Anonymous Mon 26 Feb 2018 17:56:54 No.9546327 Report

Quoted By: >>9546405

>>9546203
But $\{(\sin t,\cos t):0\leq t\leq 4\pi\}=\{(x,y):x^2+y^2=1\}$ even though $r(t)=(\sin t,\cos t)\,,\quad 0\leq t\leq 4\pi$ isn't a parametrisation of $x^2+y^2=1$

Anonymous

Anonymous Mon 26 Feb 2018 18:01:51 No.9546335 Report

Quoted By:

>>9546102
it's mechanically amplified

Anonymous

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Anonymous Mon 26 Feb 2018 18:22:36 No.9546376 Report

Quoted By: >>9547821

Requesting pic related.

3rd (or 4th) edition of George B. Thomas's Calculus and Analytic Geometry

Anonymous

Anonymous Mon 26 Feb 2018 18:28:36 No.9546385 Report

Quoted By:

>>9537723
What is the formula to calculate the p-value of a correlation ? I'm not asking R or excel functions.

Anonymous

Anonymous Mon 26 Feb 2018 18:34:03 No.9546405 Report

Quoted By:

>>9546327
Isn't it? Sure, the parametrisation contains duplicates, but is that a problem?

If you do consider it a problem, and you want a duplicate-free parametrisation, then you can additionally prove that if t in [0, 2pi] with (cos t)^2 + (sin t)^2 = 1, and s in [0, 2pi] with cos t = cos s and sin t = sin s, then t = s.

(That's not actually the case, mind you, for the correct bounds would be [0, 2pi), not [0, 2pi].)

Anonymous

Anonymous Mon 26 Feb 2018 18:50:52 No.9546447 Report

Quoted By: >>9546449 >>9546501 >>9546525 >>9546577

How can I trust scientific studies?
As a mathematician, I like that the proof for theorems is always right in front of me. Black on white. I can confirm whether someone's proof is right or wrong. But in (((natural scienes)))? Not so much. If a scientist says global warming is caused by humans, how would i know whether that's true or not? Especially because the interpretation of experiments can be biased. E.g. a scientist could say "Japanese people are short, and Japanese people live long, therefore based on our 'study', short people live long"

Anonymous

Anonymous Mon 26 Feb 2018 18:52:18 No.9546449 Report

Quoted By: >>9546455

>>9546447
>I can confirm whether someone's proof is right or wrong.
Is Mochizuki's proof of abc conjecture right or wrong?

Anonymous

Anonymous Mon 26 Feb 2018 18:55:22 No.9546455 Report

Quoted By: >>9546463

>>9546449
Yes.

Anonymous

Anonymous Mon 26 Feb 2018 18:59:38 No.9546463 Report

Quoted By: >>9546479

>>9546455
>Yes.
Why?

Anonymous

Anonymous Mon 26 Feb 2018 19:05:38 No.9546479 Report

Quoted By: >>9546494

>>9546463
Because the internal logic of our universe is classical.

Anonymous

Anonymous Mon 26 Feb 2018 19:12:12 No.9546494 Report

Quoted By:

>>9546479
>Because the internal logic of our universe is classical.
[citation needed]

Anonymous

Anonymous Mon 26 Feb 2018 19:14:21 No.9546501 Report

Quoted By:

>>9546447
You would probably enjoy reading Karl Popper

Anonymous

Anonymous Mon 26 Feb 2018 19:15:47 No.9546506 Report

Quoted By:

>>9545805
Thanks

Anonymous

Anonymous Mon 26 Feb 2018 19:20:00 No.9546525 Report

Quoted By: >>9546540

>>9546447
You're a mathematician who has never heard about statistics? Sounds fishy

Anonymous

Anonymous Mon 26 Feb 2018 19:24:55 No.9546540 Report

Quoted By:

>>9546525
It's understandable that a mathematician might not have heard about something unrelated to mathematics.

Anonymous

Anonymous Mon 26 Feb 2018 19:39:15 No.9546574 Report

Quoted By: >>9546582 >>9546590 >>9546599

Honest question, if multiplication is just addition, why doesn't anyone explain multiplying two negstives as such;
3 x 4 = 12
3 + 3 + 3 + 3 = 12

(-3)x(-4) = 12
-(-3)+(-(-3))+(-(-3))+(-(-3)) = 12

Why do they give other explanations like debt and such? Isn't the above example easier to imagine?

Anonymous

Anonymous Mon 26 Feb 2018 19:40:21 No.9546577 Report

Quoted By:

>>9546447
>How can I trust scientific studies?
In general? You shouldn't.

Anonymous

Anonymous Mon 26 Feb 2018 19:43:23 No.9546582 Report

Quoted By: >>9546589 >>9546595

>>9546574
Multiplication (of natural numbers) is just repeated addition (of natural numbers). Integers are constructed as pairs of natural numbers. Rationals are constructed as pairs of integers. Reals are constructed as sequences of rationals. I leave the rest to your imagination.

>why do they give other explanations like debt
Because constructions of integers, rationals, and reals from first principles is not very illuminating to grade school kids who are being taught arithmetic.

Anonymous

Anonymous Mon 26 Feb 2018 19:46:08 No.9546589 Report

Quoted By: >>9546599 >>9546635

>>9546582
I can't remember being taught why two negatives make a positive in grade school, only to acceppt it as a fact.

Anonymous

Anonymous Mon 26 Feb 2018 19:46:17 No.9546590 Report

Quoted By: >>9546595

>>9546574
Because debt makes more immediate use.

Anonymous

Anonymous Mon 26 Feb 2018 19:49:23 No.9546595 Report

Quoted By:

>>9546590
>>9546582
Sure, but even online I can't find the above explanation, even though it makes more sense, since two minuses make a plus.

Anonymous

Anonymous Mon 26 Feb 2018 19:52:45 No.9546599 Report

Quoted By: >>9546745 >>9547071 >>9547982

>>9546574
>-(-3)+(-(-3))+(-(-3))+(-(-3)) = 12
>Isn't the above example easier to imagine?
Not really. It will get the children confused and ask question like "are you sure that first minus is correct? it's supposed to be minus 3, right? wait my brain hurts" and etc.
>>9546589
I think kids don't give a shit. I went through the entire school without ever learning how to actually calculate the root of a number (without learning it by heart). Nobody else asked that question either

Anonymous

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Anonymous Mon 26 Feb 2018 20:02:07 No.9546623 Report

Quoted By: >>9546657 >>9546798

I failed calc II twice and just got my first test back for my third attempt, 40%
What do I keep doing wrong? I study for days and days at a time, I do the study guides, I go over forumlas, the flash cards, everything. Is this course just poorly designed or am I 4 years into college for EE, all for naught? I completely understand all the concepts taught to us, integration by parts, trig subs, series and sequences, convergence tests, improper integrals and limits, everything. Even volumes, it all makes perfect sense in my head but the second I get started on the test all the formulas are just gone like magic. Is there some reason they don't just give us some identities at least or something? It's not like we won't be without them in any real life scenario. There has to be something else I can do just to get the units for this badly designed course

Anonymous

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Anonymous Mon 26 Feb 2018 20:03:12 No.9546626 Report

Quoted By:

>>9546307
guys please, I have kot pics

Anonymous

Anonymous Mon 26 Feb 2018 20:05:04 No.9546635 Report

Quoted By: >>9547071

>>9546589
This question is either very deep or very shallow.

One way to look at it is: it is just how we define it. So you were told to memorize it because that's just how it is.

Another way to look at it is that there are no negative numbers, just the element -1. So -3 is some kind of shorthand for (-1)(3). Well, multiplication by 3 is easy to understand, it just sort of stretches out the number line so 1 goes to 3, 2 goes to 6, etc. Then we have to understand what we mean by "scaling by -1". In this case we mean we flip the number line by mirroring it around 0. And a flip of a flip is just the original thing under this kind of symmetry.

Anonymous

Anonymous Mon 26 Feb 2018 20:17:19 No.9546657 Report

Quoted By: >>9546658

>>9546623
Sounds more like you're only understanding the "what", not the "how". Have you derived any if the "formulas" or identities on your own?

Anonymous

Anonymous Mon 26 Feb 2018 20:20:13 No.9546658 Report

Quoted By:

>>9546657
That's the only thing I get right on tests

Anonymous

Anonymous Mon 26 Feb 2018 20:44:59 No.9546689 Report

Quoted By: >>9546865

$\int_{-C}F\cdot dr=\int_a^b F(r(a+b-t))r'(a+b-t) dt=-\int_b^a F(r(t))r'(t) dt=\int_C F\cdot r$
What am i doing wrong? i thought opposite orientation of a curve made the integral negative

Anonymous

Anonymous Mon 26 Feb 2018 21:13:48 No.9546745 Report

Quoted By:

>>9546599
Can you do it in your head? I always draw it on paper

Anonymous

Anonymous Mon 26 Feb 2018 21:31:45 No.9546798 Report

Quoted By: >>9546945 >>9547206

>>9546623
How are you 4 years into EE without having passed calc 2? Calc 2 was a pre-req for almost anything upper division EE for me

Anonymous

View Same Google iqdb SauceNAO 1391335851512.png, 253KiB, 329x305

Anonymous Mon 26 Feb 2018 21:37:03 No.9546807 Report

Quoted By: >>9546814 >>9546816 >>9546830 >>9548829

Why go to college if most of the time you're teaching yourself?

Anonymous

Anonymous Mon 26 Feb 2018 21:39:33 No.9546814 Report

Quoted By:

>>9546807
For the piece of paper you receive at the end.
That may not mean much where you are arguing with machines at work but it is a insurance when you work with other human beings.

Anonymous

Anonymous Mon 26 Feb 2018 21:39:41 No.9546816 Report

Quoted By:

>>9546807
you get a paper at the end, and some first connections in the academia world if you're interested in working in academia

Anonymous

Anonymous Mon 26 Feb 2018 21:40:36 No.9546823 Report

Quoted By:

What books do I need to read before I can built a small induction furnace for home projects?

Anonymous

Anonymous Mon 26 Feb 2018 21:44:16 No.9546830 Report

Quoted By:

>>9546807
this is easy: because someone who knows the topic can give you pointers in the right direction

the real question is why we would pay $10k to $40k a year for that

Anonymous

View Same Google iqdb SauceNAO asdasa.png, 122KiB, 1894x821

Anonymous Mon 26 Feb 2018 21:59:58 No.9546857 Report

Quoted By:

Anyone here good with multisim, how the fuck do I fix this shit?

Anonymous

Anonymous Mon 26 Feb 2018 22:02:10 No.9546865 Report

Quoted By: >>9546935

>>9546689
It does, the question is what the fuck is that second equal sign is supposed to represent.

Anonymous

Anonymous Mon 26 Feb 2018 22:29:08 No.9546927 Report

Quoted By: >>9546948

why is my window.innerHeight size only 512 on my phone, when the phone has a screen of 720 x 1280? when i take a screenshot, the screen is also 720 x 1280 and measuring the height manually with paint reveals 1024. happens on an android acer liquid z630s. my friends iphone has the same problem.

if i manually set some box to 256 pixel, it actually does make up exactly half of the browser height.

Anonymous

Anonymous Mon 26 Feb 2018 22:32:56 No.9546935 Report

Quoted By: >>9546961

>>9546865
from the second to third integral? integration by substitution. that's actually where i think i'm making the mistake, though i don't know why

Anonymous

View Same Google iqdb SauceNAO EF6C8FB5-51C6-4050-BA6D-597BC8ED (...).gif, 357KiB, 480x270

Anonymous Mon 26 Feb 2018 22:36:24 No.9546945 Report

Quoted By: >>9546999 >>9547190

>>9546798
I've taken and passed literally everything but my upper division classes, upper division generals included. Materials engineering, statics, chem 101, mechanical physics, it's just that one piece of shit class that's walling me

Anonymous

Anonymous Mon 26 Feb 2018 22:37:28 No.9546948 Report

Quoted By: >>9546962

>>9546927
EDIT: i also tested the width now...
phone held vertically: 512 x 360
phone held horizontally: 280 x 598

why is that happening. the numbers are swapped and they are also too small

Anonymous

Anonymous Mon 26 Feb 2018 22:42:50 No.9546961 Report

Quoted By:

>>9546935
that's what I'd assume too.

Anonymous

Anonymous Mon 26 Feb 2018 22:42:50 No.9546962 Report

Quoted By:

>>9546948
EDIT 2: i tested it on a complete blank page again. now the dimensions for holding the phone vertical are 980x1394. my screen isnt even that big

Anonymous

Anonymous Mon 26 Feb 2018 22:58:38 No.9546999 Report

Quoted By: >>9547010 >>9547072

>>9546945
Why are you taking statics and mechanical physics for EE?

Anonymous

Anonymous Mon 26 Feb 2018 23:02:22 No.9547010 Report

Quoted By:

>>9546999
Ask the retards who run my school that

Anonymous

Anonymous Mon 26 Feb 2018 23:38:00 No.9547065 Report

Quoted By:

>>9538055
26 is (4n+2)/(3n+5) from 0 to n

Anonymous

Anonymous Mon 26 Feb 2018 23:39:41 No.9547071 Report

Quoted By: >>9547519

>>9546599
>I went through the entire school without ever learning how to actually calculate the root of a number (without learning it by heart).
There's no "nice" way to find the root of a number, even if the root is an integer. The best we have are iterative approaches like Newton's method, which are not really something that a kid would understand

>>9546635
That's wrong, negative times negative being positive is not a definition, but a consequence of the axioms used to define integers
Here is a proof
https://math.stackexchange.com/questions/878836/product-of-two-negative-numbers-is-positive

Anonymous

Anonymous Mon 26 Feb 2018 23:39:48 No.9547072 Report

Quoted By: >>9547076

>>9546999
Every school makes engineering students take Physics 1 and 2.

Anonymous

Anonymous Mon 26 Feb 2018 23:41:23 No.9547076 Report

Quoted By:

>>9547072
I never took upper division statics (or a dedicated statics class in general) at Stanford for EE

Anonymous

Anonymous Mon 26 Feb 2018 23:48:44 No.9547094 Report

Quoted By: >>9547814

if my math undergrad is moving too fast (i can solve almost everything but i just run out of time) should I just forget about grad school and go into industry then

Anonymous

Anonymous Mon 26 Feb 2018 23:50:49 No.9547097 Report

Quoted By:

I'm a little confused on finding the coefficient of some term when an expression is expanded, for example I'm pretty sure that:

x^2 y^3 z^4 in the expansion of (x + y + z)^9 would be {9 choose 2} {7 choose 3} {4 choose 4} which is 9! over 2!3!4!, right?

So how would I find the coefficient of some term when an integer is involved in the expression, for example:

Find the coefficient of term x^4 y^6 when (3x + y)^10 is expanded.

Anonymous

Anonymous Tue 27 Feb 2018 00:40:49 No.9547190 Report

Quoted By:

>>9546945
With the amount of math that should be in EE though, you shouldn't be that far into your degree given that a lot of your classes should be calculus based unless you are able to take differential equations, calculus III, etc. without having calculus II.
If you don't mind me asking, what uni do you go to anon?

Anonymous

Anonymous Tue 27 Feb 2018 00:47:13 No.9547201 Report

Quoted By: >>9547203

is there a way of finding the equilibrium constant other than just reading the Kp value from a table or reading the entropy/enthalpy values>gibbs and getting it that way?

I want to have a solution where no values are just lifted from some experimental data somewhere, is it possible?

Anonymous

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Anonymous Tue 27 Feb 2018 00:48:16 No.9547203 Report

Quoted By:

>>9547201
forgot pic

Anonymous

Anonymous Tue 27 Feb 2018 00:50:50 No.9547206 Report

Quoted By:

>>9546798
Because he isn't EE but CS.

Anonymous

View Same Google iqdb SauceNAO LIGHTNINGMACHINE.jpg, 131KiB, 691x535

Anonymous Tue 27 Feb 2018 00:55:02 No.9547213 Report

Quoted By: >>9547238 >>9547268 >>9547504 >>9549550

I need fucking help guys. I'm getting into probability(easy subject I know) but for some reason my brain is stopping me from finding out the answer. It's as if it wants me to be a brainlet forever. Someone please explain this to me. Also, I would appreciate it if you turned this into an equation as well. Thank you smart ones...

Anonymous

Anonymous Tue 27 Feb 2018 01:08:09 No.9547238 Report

Quoted By: >>9547550

>>9547213
1 - P[none of them do]

Anonymous

Anonymous Tue 27 Feb 2018 01:28:46 No.9547268 Report

Quoted By:

>>9547213
50% - either one person does or they don't

Anonymous

Anonymous Tue 27 Feb 2018 02:36:46 No.9547414 Report

Quoted By:

Are there any Linear Algebra books written assuming you already know Abstract Algebra? Is there any meaningful difference when you generalize from matrices over R/C to matrices over any field?

Really I particularly want to get very good with matrices over GF( $2^n$ )

Anonymous

Anonymous Tue 27 Feb 2018 03:10:25 No.9547497 Report

Quoted By: >>9547640

I had some conceptual questions about a class and tried to go to office hours but the building my professor holds them in was locked. Is it a faux pas to just email my questions with maybe a note that if she'd rather discuss them in person I'll just try to get to office hours again next week?

Anonymous

Anonymous Tue 27 Feb 2018 03:14:02 No.9547504 Report

Quoted By: >>9547529

>>9547213
are separate strikes considered independent events?

Anonymous

Anonymous Tue 27 Feb 2018 03:20:27 No.9547519 Report

Quoted By: >>9548092

>>9547071
>that's wrong
Distinction without a difference.

Anonymous

Anonymous Tue 27 Feb 2018 03:23:32 No.9547529 Report

Quoted By: >>9547550

>>9547504
I think so.

I dunno. I feel like it's 50% but then again I feel like it should be higher. It's asking for AT LEAST one paralyzed individual, so I think that means every possibility as long as it's not 0/5 non-paralyzed. I dunno, probability is a bitch.

Anonymous

Anonymous Tue 27 Feb 2018 03:34:50 No.9547550 Report

Quoted By: >>9547612

>>9547529
dude it's way more than 50%. listen to this guy >>9547238

Anonymous

Anonymous Tue 27 Feb 2018 04:13:22 No.9547612 Report

Quoted By: >>9547629

>>9547550
How is it 1-P though? (ugh sorry im taking up this thread, this question is getting on my nerves and it's making me feel like an idiot)

Anonymous

Anonymous Tue 27 Feb 2018 04:28:32 No.9547629 Report

Quoted By: >>9547657

>>9547612
It's 1 - {the probability that no one gets shocked}.

So there's a 50% chance that the first person doesn't get shocked. There's also a 50% chance that the second person doesn't get shocked, so there's a (50%)*(50%) = 25% chance that neither of them gets shocked. There's a 50% chance that the third person doesn't get shocked, so there's a (25%)*(50%) = 12.5% chance that none of the first 3 people get shocked. Doing the same thing for the next 2 people gets us a 3.125% chance that no one gets shocked.

We know that either (no one gets shocked) or (at least one person gets shocked). It's impossible for both to be true and it's impossible for neither to be true. Therefore, if we add the probabilities of those together we must get 1. From this we can infer that 1 - (probability that no one gets shocked) = (probability that at least one person gets shocked) = 100% - 3.125% = 96.875%.

You should pick up a book on probability and study discrete probability distributions, at least a bit. This problem is a specific case of the binomial distribution https://en.wikipedia.org/wiki/Binomial_distribution.

Anonymous

Anonymous Tue 27 Feb 2018 04:33:20 No.9547640 Report

Quoted By:

>>9547497
not at all

Anonymous

Anonymous Tue 27 Feb 2018 04:40:38 No.9547657 Report

Quoted By:

>>9547629
Thank you, I finally get it now. I've been reading up on probability but I haven't really gotten that far. I need a lot of catching up to do.

Anonymous

View Same Google iqdb SauceNAO brainlettttt.jpg, 41KiB, 800x450

Anonymous Tue 27 Feb 2018 05:56:04 No.9547797 Report

Quoted By: >>9548490

I am currently making an experiment of the resonant frequency of wine glasses and how they change based on the volume of water in them. Is it possible to calculate the amount of energy absorbed by the water if I only know the frequency of the sound wave with and without the water?

Anonymous

Anonymous Tue 27 Feb 2018 06:02:32 No.9547814 Report

Quoted By:

>>9547094
No but you should practice more under similar conditions, dipshit

Anonymous

Anonymous Tue 27 Feb 2018 06:06:04 No.9547821 Report

Quoted By:

>>9546376
Anyone?

Anonymous

Anonymous Tue 27 Feb 2018 08:28:54 No.9547982 Report

Quoted By:

>>9546599
> I went through the entire school without ever learning how to actually calculate the root of a number
We learnt the Babylonian method, but only in the context of the construction of the reals (it generates a sequence of rationals whose limit is typically irrational).

Being able to calculate square roots by hand is fairly pointless. Before calculators were ubiquitous, you'd typically use 10^(log10(x)/2), which is trivial with either a slide rule or log tables. If you need arbitrary precision, you'd use this:
en.wikipedia.org/wiki/Methods_of_computing_square_roots#Decimal_%28base_10%29

Anonymous

Anonymous Tue 27 Feb 2018 10:51:19 No.9548092 Report

Quoted By:

>>9547519
There is a difference between "we defined negative times negative to be positive" and "we defined an arithmetic system and in this system (as a consequence of our definitions) negative times negative is positive"

Anonymous

Anonymous Tue 27 Feb 2018 15:07:50 No.9548372 Report

Quoted By: >>9548374 >>9548512

Does the integral
$f(x) = \frac{1}{\sqrt{2}}\int_{-\infty}^\infty dx e^{-\frac{1}{2!}-\frac{\alpha}{4!}x^4}$ ,
have a closed form of any sort?

Anonymous

View Same Google iqdb SauceNAO 1507483926815[1].png, 30KiB, 406x452

Anonymous Tue 27 Feb 2018 15:09:02 No.9548374 Report

Quoted By:

>>9548372
obviously
$f(x) = \frac{1}{\sqrt{2}}\int_{-\infty}^\infty dx e^{-\frac{1}{2!}x^2-\frac{\alpha}{4!}x^4}$ ,
my mistake.

Anonymous

Anonymous Tue 27 Feb 2018 15:18:21 No.9548384 Report

Quoted By:

>>9542614
Looking more closely, I think this is needlessly complicated. Wolfram alpha gives simple answers for exp(pi i 36/180) and exp(pi i 35 /180), so getting exp(pi i 1/180) is pretty simple. Should get all values with just a few roots.

Anonymous

View Same Google iqdb SauceNAO A problem.png, 23KiB, 750x538

Anonymous Tue 27 Feb 2018 16:21:46 No.9548480 Report

Quoted By: >>9548482

I'm stuck on this problem. (For some context, the text being used is Royden - roughly 6.1-6.2)

For part a) is it sufficient to say that since the terms are nonnegative, f(x) is increasing?

For part b) is the argument a standard continuity argument with |s_i - x_i|?

For part c) do we have to start by using Lebesgue's Theorem to state f(x) is differentiable almost everywhere?

Mainly, I'm trying to find where Lebesgue's and Vitali's follows in the grand scheme of this.

Sorry for the long question and I'm not looking for a full proof but rather an approach that might be useful. I appreciate any help I may recieve.

Anonymous

Anonymous Tue 27 Feb 2018 16:23:17 No.9548482 Report

Quoted By:

>>9548480
Vitali's covering lemma I meant to say. In case there are other Vitali's lemmas that mean something else.

Anonymous

Anonymous Tue 27 Feb 2018 16:26:01 No.9548490 Report

Quoted By:

>>9547797
someone plz im retarded

Anonymous

Anonymous Tue 27 Feb 2018 16:36:39 No.9548512 Report

Quoted By: >>9548516

>>9548372
I apologize in advance if what I say leads you in the wrong direction, but f(x) vaguely resembles the gamma function (other than the - \infty to 0 part which may perhaps be accounted for with a second term).

Could there be an expression in the form of 1/2^{1/2} * s! * t! ?

Anonymous

Anonymous Tue 27 Feb 2018 16:39:05 No.9548516 Report

Quoted By:

>>9548512
My mistake; I meant to write in the form of 1/2^{1/2} * (s! + t!)

Anonymous

Anonymous Tue 27 Feb 2018 19:32:35 No.9548829 Report

Quoted By:

>>9546807
Depends on the field. Normally its for the sheet of paper. In the case of math, its for knowing what to teach yourself.

Anonymous

Anonymous Wed 28 Feb 2018 00:12:55 No.9549550 Report

Quoted By:

>>9547213
I think it's 97%

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