Question

Find the derivative of cos 2x​

Answer 1

2sin2x

Explanation:

let u= 2x

du/dx =2

y=cos2x

y=cosu

dy/du =sinu

dy/dx =dy/du × du/dx

dy/dx = sinu × 2

dy/dx =2sinu

but, u=2x

hence dy/dx = 2sin2x