# Asmar, problem 2.2-5, f(x)=|x| F:=(m,x)->(4/Pi)*(1/(2*m+1)^2)*cos(2*m*x+x); S:=(N,x)->Pi/2-sum(F(m,x),m=0..N): opts:=axes=boxed,thickness=2: n:=20:plot(S(n,x),x=-2*Pi..3*Pi,opts);S(n,x);