-atan(3*x)
-3 -------- 2 1 + 9*x
54*x ----------- 2 / 2\ \1 + 9*x /
/ 2 \ | 36*x | -54*|-1 + --------| | 2| \ 1 + 9*x / ------------------- 2 / 2\ \1 + 9*x /