Question

What is the derivative of `cos^2x`?

Answer 1

`(d y)/(d x)=-2cos x sin x`

Explanation:

`y=cos^2x`

`cos x=u`

`y=u^2`

`(d y)/(d u)=2u=2cosu`

`(d u)/(d x)=-sin x`

`(d y)/(d x)=(d y)/(d u)*(d u)/(d x)`

`(d y)/(d x)=-2cos x sin x`