Find ddx[arctan(2x)]\frac{d}{dx}[\arctan(2x)]dxd[arctan(2x)].
21+4x2\frac{2}{1+4x^2}1+4x22
11+4x2\frac{1}{1+4x^2}1+4x21
21+2x2\frac{2}{1+2x^2}1+2x22
11−4x2\frac{1}{\sqrt{1-4x^2}}1−4x21