How to solve an equation with a variable that has multiple values

Hello, I can't solve the attached equation for two specific variables using two loops on matlab.

with: loop1 for x1 and x3 = 0 to 1000 and loop2 for m and n = 0 to 10,

a = b =1000; and Teta(mn) = 0.1

Either way, any help would be greatly appreciated!

[Dyuman Joshi]

What have you tried yet? Show your attempt and ask a specific question where you are having trouble.

[Torsten]

For a fixed value for theta_mn (in your case 0.1), the infinite series won't converge.

[issam BEN SALAH]

Hello Dyuman,

Thanks for this answer, i try this script as follow, but I want the oscillation in the interval [400 600] to be around 0.1 only (like the gibbs phenomen)

clear all, close all
r=1e-0;
a=1000*r;   b=a;   pasx=r;   pasy=pasx;
x0=500*r;
z0=500*r;
c=100*r;
d=100*r;
x1_int=x0-c; x1_fin=x0+c;
x3_int=z0-d; x3_fin=z0+d;
x111=0:pasx:a;
x333=0:pasy:b;
tethh=zeros(length(x111),length(x111));
i=0;
for x1=0:pasx:1000
   i=i+1;
    tethy=[];
    j=0;
    for x3=0:pasy:1000
       j=j+1;
       if x1>=400 & x1<=600 &  x3>=400 & x3<=600
           teth=0;
           for m=0:10
               for n=0:10
                  c=cos(((m*pi)/a)*x1); 
                  s=sin(((n*pi)/b)*x3);
                  teth=sum(sum(abs(Omn*c*s)));
               end
           end
           tethh(i,j)=teth;
           clear teth
       else
           tethh(i,j)=0;
    end
end
figure(1)
meshc(x333,x111,tethh)
axis tight
shading interp
grid on,xlabel('x_1 (nm)'),ylabel('x_3 (nm)'),zlabel('\theta (K)'),colormap('jet'),colorbar
figure(2)  
plot(x111,tethh(401,:))

[issam BEN SALAH]

Hello Torsten,

Utmost thank you for response, I want to run the oscillation in the interval [400 600] to be around 0.1 only (like the gibbs phenomen).