2 2*x 1 - ------ 2 1 + x ---------- 2 1 + x
(1.0 - 2.0*x^2/(1.0 + x^2))/(1.0 + x^2)
2 1 - x --------- 2 / 2\ \1 + x /
-(1 + x)*(-1 + x) ------------------ 2 / 2\ \1 + x /
/ 2\ -\-1 + x / ------------- 4 2 1 + x + 2*x