# How do you find the derivative of 2 sin x + sin 2x?

By using $\mathrm{ds} \in u = \mathrm{du} \cos u$
$f \left(x\right) = 2 \sin x + \sin 2 x$
$f ' \left(x\right) = 2 \cos x + 2 \cos 2 x$