[QUOTE=Quacky;694202]Let's see.

$\displaystyle y = \sqrt{arctan2x}$

$\displaystyle y^2 = arctan2x$

$\displaystyle tany^2 = 2x$

$\displaystyle \frac {dy}{dx} * sec^2y^2$ $\displaystyle tany^2 = 2$

How do I differentiate from here? I get $\displaystyle \frac {dy}{dx} = \frac {1}{4x^3+x}$ as an answer