x*acos(-x)
x ----------- + acos(-x) ________ / 2 \/ 1 - x
2 x 2 + ------ 2 1 - x ----------- ________ / 2 \/ 1 - x
/ 2 \ | 3*x | x*|4 + ------| | 2| \ 1 - x / -------------- 3/2 / 2\ \1 - x /