Find the derivative of f(x)=arctan(x)f(x) = \arctan(x)f(x)=arctan(x).
11+x2\frac{1}{1+x^2}1+x21
11−x2\frac{1}{1-x^2}1−x21
x1+x2\frac{x}{1+x^2}1+x2x
1x2+1\frac{1}{x^2+1}x2+11