atan(9*x)
9 --------- 2 1 + 81*x
-1458*x ------------ 2 / 2\ \1 + 81*x /
/ 2 \ | 324*x | 1458*|-1 + ---------| | 2| \ 1 + 81*x / --------------------- 2 / 2\ \1 + 81*x /