I=tan−11+x1−x
Let x=cosθ⇒dx=−sinθdθ
I=∫tan−11+cosθ1−cosθ(−sinθdθ)
=−∫tan−12cos22θ2sin22θsinθdθ
=−∫tan−1tan2θ.sinθdθ
=−21∫θ.sinθdθ
=−21[θ.(−cosθ)−∫1.(−cosθ)dθ]
=−21[−θcosθ+sinθ]
=+21θcosθ−21sinθ
=21cos−1x.x−211−x2+C
=2xcos−1x−211−x2+C
=21(xcos−1x−1−x2)+C