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