Which of the following functions has a derivative equal to 1x2+1\frac{1}{x^2+1}x2+11?
ln(x2+1)\ln(x^2+1)ln(x2+1)
arctan(x)\arctan(x)arctan(x)
arcsin(x)\arcsin(x)arcsin(x)
12x\frac{1}{2x}2x1