/ 2\ \1 + x /*acot(x) ---------------- 2
((1 + x^2)*acot(x))/2
-1/2 + x*acot(x)
x - ------ + acot(x) 2 1 + x
/ 2 \ | x | 2*|-1 + ------| | 2| \ 1 + x / --------------- 2 1 + x