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