> restart;

> u50 := (x,y) -> Sum(-8/(n*n*Pi)*sin(n/2*Pi) * exp( -7/4 * n*n*y)*sin(n/2*x) ,n=1..50);

> plot3d( u50(x,y), x=0..2*Pi, y=0..2, labels =[`x`, `time`, `u(x,t)`], axes=FRAMED, style=patch);

> v6 := (x,y) -> Sum(-8/(n*n*Pi)*sin(n/2*Pi) * exp( -7/4 * n*n*y)*sin(n/2*x) ,n=6..10);

> plot3d( v6(x,y), x=0..2*Pi, y=0..2, labels =[`x`, `time`, `u(x,t)`], axes=FRAMED, style=patch);

>

> v60 := (x,y) -> Sum(-8/(n*n*Pi)*sin(n/2*Pi) * exp( -7/4 * n*n*y)*sin(n/2*x) ,n=60..70);

> plot3d( v60(x,y), x=0..2*Pi, y=0..2, labels =[`x`, `time`, `u(x,t)`], axes=FRAMED, style=patch);

>