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 /