Hey, so I developed this code to try a simulation on chladni patterns and the wave equation of vibrating plates.

So here's my code so far

X = 1;

Y = 1;

k1 = n*\[Pi]/X;

k2 = m*\[Pi]/Y;

k = c*\[Pi]*Sqrt[(n/X)^2 + (m/Y)^2];

nmax = 10;

mmax = 10;

Manipulate[

Plot3D[Sum[

Sin[k1*x]*Sin[k2*y]*Cos[k * t], {n, 1, nmax}, {m, 1, mmax}], {x, -X/

2, X/2}, {y, -Y/2, Y/2}], {t, 0, 20}]

edit: i forgot to put a value to constant "c"

now i put "c=1;" and the part of Cos[k*t] now only has values of {1;-1} somehow

The problem is that it doesn't work for t>0 somehow.

I know there's probably some bug there, but I can't see where.