Given f(x)=arctan(x)f(x) = \arctan(x)f(x)=arctan(x), find f′′(x)f''(x)f′′(x).
11+x2\frac{1}{1+x^2}1+x21
−2x(1+x2)2\frac{-2x}{(1+x^2)^2}(1+x2)2−2x
1(1+x2)2\frac{1}{(1+x^2)^2}(1+x2)21
−1(1+x2)2\frac{-1}{(1+x^2)^2}(1+x2)2−1