?animate
with(plots);
animate(plot, [sin(t*x),x=0..2*Pi],t=0..3);
assume(n,integer);
b:=n->1/4*int((x-3)*sin(n*Pi*x/8),x=3..4)+1/4*int((5-x)*sin(n*Pi*x/8),x=4..5);
b(1);
plot(sum(b(n)*sin(n*Pi*x/8),n=1..100),x=0..8);
animate(plot,[sum(b(n)*cos(Pi*n*t/8)*sin(n*Pi*x/8),n=1..100),x=0..8],t=0..20,frames=100);