/sci/ - Science & Math » Thread #11025682

18KiB, 262x300, Duff_Beer-logo-A7BA6E5125-seeklogo.com.png

View Same Google iqdb SauceNAO

Anonymous Wed 02 Oct 13:48:54 2019 No.11025682 View Reply Original Report

Quoted By: >>11025750

Is it normal that this is the first thing that comes to my mind when I see the notation for the directional derivative?

Anonymous

Anonymous Wed 02 Oct 2019 14:10:52 No.11025750 Report

Quoted By: >>11025793 >>11026021

>>11025682
>directional derivative

Sounds like some gay engineering shit. Care to fill me in?

Anonymous

Anonymous Wed 02 Oct 2019 14:34:26 No.11025793 Report

Quoted By: >>11025811

>>11025750
for a function $f:\mathbf{R}^n\to\mathbf{R}$ , the directional derivative is $\nabla_\mathbf{e}f(\mathbf{x})=(\hat{\mathbf{e}}\cdot\nabla)f(\mathbf{x})=\nabla f(\mathbf{x})\cdot\hat{\mathbf{e}}$ where e hat is in any direction of your choice. So yeah, it's gay (cool) engi shit.

I don't know the notation OP is talking about.

Anonymous

Anonymous Wed 02 Oct 2019 14:43:49 No.11025811 Report

Quoted By: >>11025838

>>11025793
You are writing it in terms of itsdefinition as gradient dotted into unit vector but the notation for the directional derivative is capital D sub u vector f.

Anonymous

Anonymous Wed 02 Oct 2019 14:54:18 No.11025838 Report

Quoted By: >>11026021

>>11025811
Nabla sub u is a perfectly valid and common notation as well

Anonymous

Anonymous Wed 02 Oct 2019 16:49:36 No.11026021 Report

Quoted By:

>>11025838
>Nabla sub u is a perfectly valid and common notation as well
No. It makes no sense for functions from R^n to R^(>1). Let f be a function from R^2 to R^2. What even is the gradient? $D_{v}f$ is the only acceptable notation for directional derivatives.

>>11025750
It's just the derivative of a function along the direction of some vector v and you should have learned this on calc 3.

Anonymous

Anonymous Wed 02 Oct 2019 21:32:44 No.11026616 Report

Quoted By:

$D_{\vec{u}} ff$

Capcode	All Only User Posts Only Moderator Posts Only Admin Posts Only Developer Posts
Show Posts	All Only With Images Only Without Images
Deleted Posts	All Only Deleted Posts Only Non-Deleted Posts
Ghost Posts	All Only Ghost Posts Only Non-Ghost Posts
Post Type	All Only Sticky Threads Only Opening Posts Only Reply Posts
Results	All Grouped By Threads
Order	Latest Posts First Oldest Posts First

Your latest searches