acos(1 - x)
1 ----------------- ______________ / 2 \/ 1 - (1 - x)
-1 + x ----------------- 3/2 / 2\ \1 - (1 - x) /
2 3*(-1 + x) 1 + ------------ 2 1 - (1 - x) ----------------- 3/2 / 2\ \1 - (1 - x) /