>	restart:with(plots):

 

>	Sn:=(x,n)->2/Pi*sum(4*k/(4*k^2-1)*sin(2*k*x),k=1..n);

 

>	plt1:=plot(cos(x),x=-Pi..2*Pi,color=blue,thickness=2,view=[-Pi..2*Pi,-2..2]):

 

>	animate(plot,[Sn(x,n),x=-Pi..2*Pi,color=red,thickness=2],n=1..30,frames=30,background=plt1);