2 atan (x)
atan(x)^2
2*atan(x) --------- 2 1 + x
2*(1 - 2*x*atan(x)) ------------------- 2 / 2\ \1 + x /
/ 2 \ | 3*x 4*x *atan(x)| 4*|-atan(x) - ------ + ------------| | 2 2 | \ 1 + x 1 + x / ------------------------------------ 2 / 2\ \1 + x /