Why won't Mathematica plot this?

Questions
1

I need to use Mathematica to plot the sum (image attached) but for some reason when I hit run nothing happens. Is there some small mistake I made that I’m overlooking?

Open in Wolfram Cloud ↗
2

Give a value to m (it is blue, so nothing is assigned to it)

3

What would be the syntax for that? I have tried {x, 0,1}, {y,0,1}, {m, 50} and {x, 0,1}, {y,0,1}, {50} as well as {x, 0,1}, {y,0,1}, {m = 50}.

4

Plot3D[u[x, y, 50], {x, 0, 1}, {y, 0, 1}]

5

Thank you, sorry if that was a very trivial question. Unfortunately the code still won’t work, but at least I have that one issue solved.

6

Hi Sydney,

u is of the form Sum[expression, {m, n = 1}]. The syntax for the limits is incorrect. Check the documentation for Sum.

7

That’s weird. It works for me. Given Rohit’s comment, I think there must be some copy-paste weirdness. If you just use simple InputForm, I think you can avoid that:

u[x_, y_, m_] := 
 Sum[(2/Sinh[n*Pi])*((1/(n*Pi)^2)*Sin[(n*Pi)/2] + (1/(n*Pi))*
      Sin[(n*Pi)/2])*Sin[n*Pi*x]*Sinh[(1 - y)*n*Pi], {n, 1, m}];
Plot3D[u[x, y, 50], {x, 0, 1}, {y, 0, 1}]

SumPlotDemo.bmp (1.19 MB)