/sci/ - Science & Math » Thread #14407754

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Anonymous Tue 19 Apr 00:09:58 2022 No.14407754 View Reply Original Report

Quoted By: >>14411383 >>14412522 >>14413427 >>14413504 >>14413885 >>14413946 >>14414887 >>14416639 >>14416698 >>14418011 >>14418948 >>14418970 >>14420027 >>14421734

what the fuck is my professor's problem

Anonymous

Anonymous Wed 20 Apr 2022 01:18:39 No.14411383 Report

Quoted By: >>14411387 >>14416633

>>14407754
OP, use the Schur complment method:
https://en.wikipedia.org/wiki/Schur_complement#Properties
Split M into block 4x4 matrices,
>A | B
>C | D
Then Det M = (Det A) (Det (D - C A^1 B))
Alternatively, get M in upper triangular form, then the determinant is the product of the diagonal entries. This second method is probably more what the prof has in mind.

Anonymous

Anonymous Wed 20 Apr 2022 01:19:41 No.14411387 Report

Quoted By:

>>14411383
Sorry, should be
Det M = (Det A) (Det (D - C A^-1 B))

Anonymous

Anonymous Wed 20 Apr 2022 01:26:12 No.14411399 Report

Quoted By: >>14411412

Upper triangular form is easy to get. Start off by shifting swapping R6 and R1 so you have a 1 in the top left, then just blast away clearing the first column. No need to divide by anything since you don't care about getting 1s down the diagonal. Just go like R2 -> R2 - 4 R4 and so on. The numbers will get large by who cares. Keep swapping rows or columns to get a convenient entry in the diagonal you're working on and keep at it.
Then when you have all zeros below the diagonal multiply the diagonal entries and you're done.

Anonymous

Anonymous Wed 20 Apr 2022 01:30:12 No.14411412 Report

Quoted By:

>>14411399
You don't have to start with swapping R6 and R1 of course, just do whatever you need to get a convenient setup for zeroing out below-diagonal entries. And don't worry about the entries growing large as you keep multiplying and combining rows, that's fine

Anonymous

Anonymous Wed 20 Apr 2022 02:51:01 No.14411691 Report

Quoted By:

>>14411318
Got a 90%. You need to grow some balls.

Anonymous

Anonymous Wed 20 Apr 2022 03:07:49 No.14411733 Report

Quoted By: >>14411762 >>14411924 >>14412226

>>14411307
Literally 90% of this thread is faggots saying “there’s a trick to it” despite not knowing what the trick is or truly knowing if there actually is one. Kill yourselves

Anonymous

Anonymous Wed 20 Apr 2022 03:20:15 No.14411762 Report

Quoted By:

>>14411733
You can do it in 28 simple row operations, give or take a few swaps

Anonymous

Anonymous Wed 20 Apr 2022 04:18:28 No.14411883 Report

Quoted By:

>>14411049
That'll just piss him off and make your life harder. Best way to deal with professors is to schmooze them. They're so used to dealing with autist phd candidates and colleagues that they won't realize you're manipulating them.

Anonymous

Anonymous Wed 20 Apr 2022 04:30:51 No.14411924 Report

Quoted By:

>>14411733
That's this board in a shellnut. Braggarts and fakers who can't actually do anything but they talk a big game.

Anonymous

Anonymous Wed 20 Apr 2022 05:58:10 No.14412084 Report

Quoted By:

>>14407827
Asians and Chinese BTFO

Anonymous

Anonymous Wed 20 Apr 2022 07:13:00 No.14412226 Report

Quoted By:

>>14411733
Just crank it out, faggot. It's just row operations. Don't like it? Think it's too boring? Eat shit.
Want a shortcut? Use Schur's Complement, to reduce it to 4x4 matrices.

Anonymous

Anonymous Wed 20 Apr 2022 07:46:09 No.14412264 Report

Quoted By: >>14412276

>>14407815
nice, still a lot of fucking steps

Anonymous

Anonymous Wed 20 Apr 2022 07:50:01 No.14412267 Report

Quoted By:

>>14408847
doing that by hand is equivalent to shoveling a mountain of shit and then shoveling it back

Anonymous

Anonymous Wed 20 Apr 2022 07:53:59 No.14412271 Report

Quoted By:

>>14407815
Holy shit that's amazing
Too bad about the unpleasantness with young Alice...
Mister Dodgson can never again show his face there

Anonymous

Anonymous Wed 20 Apr 2022 07:54:17 No.14412272 Report

Quoted By:

>>14407827
Chinks btfo'd once again.

Anonymous

Anonymous Wed 20 Apr 2022 07:55:10 No.14412276 Report

Quoted By:

>>14412264
Yeah but each one is trivial. you can just read off the subdeterminants

Anonymous

Anonymous Wed 20 Apr 2022 11:13:48 No.14412522 Report

Quoted By:

>>14407754
People used to inverse these big matrices by hand. Your prof is just sharing the tradition.

Anonymous

Anonymous Wed 20 Apr 2022 11:26:19 No.14412547 Report

Quoted By: >>14412659

Can you reduce it to a lower triangular matrix? Or it has to Gaussian elimination?

Anonymous

Anonymous Wed 20 Apr 2022 12:09:23 No.14412659 Report

Quoted By: >>14412682

>>14412547
Yeah do this but swap columns and rows until you get all the tidy looking entries up in the top left area. Send all the pozzed shit down to the bottom right.

Anonymous

Anonymous Wed 20 Apr 2022 12:22:55 No.14412682 Report

Quoted By:

>>14412659
All right. That would do. Thanks.

Anonymous

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Anonymous Wed 20 Apr 2022 15:59:45 No.14413231 Report

Quoted By: >>14413836 >>14414800

An online calculator gave me |A| = 121003124 if anyone cares.

Anonymous

Anonymous Wed 20 Apr 2022 17:35:17 No.14413427 Report

Quoted By:

>>14407754
just keep row-reducing and dilating

Anonymous

Anonymous Wed 20 Apr 2022 18:01:23 No.14413504 Report

Quoted By:

>>14407754
symbolab.com

Anonymous

Anonymous Wed 20 Apr 2022 20:18:06 No.14413836 Report

Quoted By:

>>14413231
What website

Anonymous

Anonymous Wed 20 Apr 2022 20:44:40 No.14413885 Report

Quoted By:

>>14407754
It's your problem that you don't pay attention in class.

Anonymous

Anonymous Wed 20 Apr 2022 21:24:04 No.14413946 Report

Quoted By: >>14416702 >>14417075

>>14407781
this
>>14407754
this shouldn't be hard to program, in any language
this should take less than 200 lines
let's do it

Anonymous

Anonymous Wed 20 Apr 2022 23:38:28 No.14414209 Report

Quoted By:

Use individual row operations, but use matlab or whatever to actually perform the operations to reduce error and save time.
Then just mess with it till you get triangular form.

Anonymous

Anonymous Thu 21 Apr 2022 05:23:50 No.14414800 Report

Quoted By:

>>14413231
you can use a scalar to get rid of fractions until one nice big fat division at the end. if you're doing it by hand, it's probably best to just leave the primes unmultiplied in the denominator outside of the matrix

Anonymous

Anonymous Thu 21 Apr 2022 06:21:42 No.14414867 Report

Quoted By:

>>14407815
>Dodgson (Lewis Carroll) condensation
Fucking nice.

Anonymous

Anonymous Thu 21 Apr 2022 06:45:13 No.14414887 Report

Quoted By:

>>14407754
>he doesn't align the mstrix to the left
Truly a disgusting ape.

Anonymous

Anonymous Thu 21 Apr 2022 21:52:54 No.14416633 Report

Quoted By:

>>14411383
Neat

Anonymous

Anonymous Thu 21 Apr 2022 21:58:56 No.14416639 Report

Quoted By:

>>14407754
He will destroy your ((("ADHD")))

Anonymous

Anonymous Thu 21 Apr 2022 22:19:11 No.14416698 Report

Quoted By:

>>14407754
I've seen worse matrix hijinks. Refused to finish it after realizing it would have resulted in a massive matrix spanning multiple pages.

Anonymous

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Anonymous Thu 21 Apr 2022 22:23:23 No.14416702 Report

Quoted By: >>14417075 >>14419209

>>14413946
It takes significantly less than 200 lines. This is a Python implementation of the 'by-hand' method that I was taught.

Anonymous

Anonymous Fri 22 Apr 2022 01:17:14 No.14417075 Report

Quoted By:

>>14416702
>>14413946
Codemonkeys are truly contemptible.

Anonymous

Anonymous Fri 22 Apr 2022 01:30:01 No.14417123 Report

Quoted By: >>14417296 >>14417961

I strongly believe OP just made it up. No professor would assign that because it would be a pain in the ass to actually grade.

Anonymous

Anonymous Fri 22 Apr 2022 02:39:11 No.14417296 Report

Quoted By:

>>14417123
It’s not like they’re grading the work. The work is just there to show they tried and didn’t look shit up. And like the other anon said maybe he doesn’t have bitches on his dick. No pussy whatsoever!

Anonymous

Anonymous Fri 22 Apr 2022 11:05:53 No.14417961 Report

Quoted By: >>14417963

>>14417123
You're assuming that the professor grades almost anything, except for portions of the final exam. Instead, these 'trivial' tasks a performed by an army of underpaid, malnourished, and often equally contemptible TAs.

Anonymous

Anonymous Fri 22 Apr 2022 11:06:56 No.14417963 Report

Quoted By:

>>14417961
*are performed

Anonymous

Anonymous Fri 22 Apr 2022 12:07:47 No.14418011 Report

Quoted By:

>>14407754
Excel moment

Anonymous

Anonymous Fri 22 Apr 2022 19:45:51 No.14418948 Report

Quoted By:

>>14407754
>center aligned numbers
Sickening.

Anonymous

Anonymous Fri 22 Apr 2022 19:56:44 No.14418970 Report

Quoted By:

>>14407754
kek

Anonymous

Anonymous Fri 22 Apr 2022 21:38:21 No.14419209 Report

Quoted By: >>14419674 >>14421695

>>14416702
Now make one that outputs the steps of row-reduction in latex as-if you did it by hand instead of factorial time hackwork

[spoiler:lit]I actually did this for my Linear Algebra/Diff EQ course the week we had 8 problems like OPs but smaller[/spoiler:lit]

Anonymous

Anonymous Sat 23 Apr 2022 00:35:11 No.14419674 Report

Quoted By: >>14419953

>>14419209
It's not factorial time you poltroon. You don't need to re-do columns after each one is reduced. It's just linear, it'll take like 30 steps max.

Anonymous

Anonymous Sat 23 Apr 2022 02:49:56 No.14419953 Report

Quoted By: >>14420254

>>14419674
>cofactor expansion algorithm is linear
ok chud

Anonymous

Anonymous Sat 23 Apr 2022 03:26:36 No.14420027 Report

Quoted By:

>>14407754
you're a lazy faggot

Anonymous

Anonymous Sat 23 Apr 2022 06:34:04 No.14420254 Report

Quoted By: >>14421398

>>14419953
Just row reduce it you fag
Then multiply the diagonal
No one is telling you (clueless) to do the cofactors which are obviously non-linear in scale

Anonymous

Anonymous Sat 23 Apr 2022 16:15:28 No.14421398 Report

Quoted By:

>>14420254
aight but anon's algorithm is clearly cofactor expansion

Anonymous

Anonymous Sat 23 Apr 2022 18:02:54 No.14421695 Report

Quoted By:

>>14419209
I did this for my senior capstone with reaction networks.

Anonymous

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Anonymous Sat 23 Apr 2022 18:17:48 No.14421734 Report

Quoted By:

>>14407754
That's a big matrix...

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