Find the derivative of f(x)=arctan(x2)f(x) = \arctan(x^2)f(x)=arctan(x2).
2x1+x2\frac{2x}{1+x^2}1+x22x
2x1+x4\frac{2x}{1+x^4}1+x42x
11+x4\frac{1}{1+x^4}1+x41
x21+x4\frac{x^2}{1+x^4}1+x4x2