Chain Rule Computations

Compute the following derivatives, which require the chain rule. $($Answer for $2$ nd one is $3co{s}^{2}x(-sinx)=-3cosxsinx$

$(1)\frac{d}{dx}co{s}^{2}x=\frac{d}{dx}[(cosx{)}^2]=$

$(2)\frac{d}{dx}co{s}^{3}x=\frac{d}{dx}[(cosx{)}^3]=$

$(3)\frac{d}{dx}co{s}^{m}x=($where $m$ is an integer greater than $1$ ; keep $m$ as $m)$