计算下列函数的导数.
(1)$y=\ln^2\arctan x$.
(2)$y=e^{ \sin ^{2} \frac {1}{x}} \arctan \dfrac {1 x}{1-x}$.
(3)$y=x^{\sin 2x}$.
(4)$y= \dfrac {x}{ \sqrt {x^{2} 1}}$.
$\text{A.}$ $f(x)= \dfrac {|x|}{x 1}$
$\text{B.}$ $f(x)= \sqrt { \cos x}$
$\text{C.}$ $f(x)=x \arctan \dfrac {1}{x}$
$\text{D.}$ $f(x)= \cos \sqrt {|x|}$