# What is the derivative of f(x) = cos( sin( x ))?

$f ' \left(x\right) = - \sin \left(\sin x\right) \cdot \cos x$
$f ' \left(x\right) = - \sin \left(\sin x\right) \cdot \left(\sin x\right) ' = - \sin \left(\sin x\right) \cdot \cos x$