Evaluate ddxarctan(x+11−x)\frac{d}{dx} \arctan(\frac{x+1}{1-x})dxdarctan(1−xx+1).
1/(1+x2)1/(1+x^2)1/(1+x2)
2/(1+x2)2/(1+x^2)2/(1+x2)
000
−1/(1+x2)-1/(1+x^2)−1/(1+x2)