x + atan(x)
d --(x + atan(x)) dx
1 1 + ------ 2 1 + x
-2*x --------- 2 / 2\ \1 + x /
/ 2 \ | 4*x | 2*|-1 + ------| | 2| \ 1 + x / --------------- 2 / 2\ \1 + x /