acos(9*x)
-9 -------------- ___________ / 2 \/ 1 - 81*x
-729*x -------------- 3/2 / 2\ \1 - 81*x /
/ 2 \ | 243*x | -729*|1 + ---------| | 2| \ 1 - 81*x / -------------------- 3/2 / 2\ \1 - 81*x /