kill(all)$

van=facebook.com/LearningCalculus$

f(x):=log(cot(x))$

S:'(integrate(log(cot(x)),x,0,%pi/4)) = ''(integrate(f(x),x,0,%pi/4))$

S = 0.915966;

C(n):=sum((-1)^k/(2*k+1)^2,k,0,n);

C(1000); fpprintprec:6$ float(C(1000));