cos(sin x)

Let $y = \cos (\sin x)$

$\Rightarrow$ $\cfrac{{dy}}{{dx}} = \cfrac{d}{{dx}}\cos (\sin x) = - \sin (\sin x)\cfrac{d}{{dx}}\sin x$

$= - \sin (\sin x)\cos x$

therefore $\frac{dy}{dx}= = - \sin (\sin x)\cos x$