MHB Maxima and Minima (vector calculus)

WMDhamnekar
MHB
Messages
376
Reaction score
28
Hi, Hi,

Author said If we look at the graph of $ f (x, y)= (x^2 +y^2)*e^{-(x^2+y^2)},$ as shown in the following Figure it looks like we might have a local maximum for (x, y) on the unit circle $ x^2 + y^2 = 1.$

1649834173266.png
But when I read this graph, I couldn't guess that the stated function have a local maximum on the unit circle $ x^2 + y^2=1$

1)I want to know what did author grasp in the above figure which compelled him to make the aforesaid statement?

2) How to plot this function in 'R' or in 'GNU OCTAVE' or in any graphing calculator ? Is it easy to plot $f(x,y)= (x^2+y^2)*e^{-(x^2+y^2)} ?$
 
Last edited:
Physics news on Phys.org
Do you notice that the only way x and y appear in that function is as "$x^2+y^2$"? In cylindrical coordinates we can write it as $f(r,\theta)= r^2e^{-r^2}$. If we write it as $y= x^2e^{x^2}$ its graph looks like this: <iframe src="https://www.desmos.com/calculator/oj7v5yfd0f?embed" width="500" height="500" style="border: 1px solid #ccc" frameborder=0></iframe>

Do you see what happens at x= 1 and x= -1? Imagine rotating that around the y-axis.
 
Thread 'Derivation of equations of stress tensor transformation'
Hello ! I derived equations of stress tensor 2D transformation. Some details: I have plane ABCD in two cases (see top on the pic) and I know tensor components for case 1 only. Only plane ABCD rotate in two cases (top of the picture) but not coordinate system. Coordinate system rotates only on the bottom of picture. I want to obtain expression that connects tensor for case 1 and tensor for case 2. My attempt: Are these equations correct? Is there more easier expression for stress tensor...
Back
Top