Question

find the derivative of 4cos^2x​

Answer 1

$\frac{d}{dx} (4cos^{2}x) = 4 \frac{d}{dx}(cos^{2}x) \\ = 4 \times 2cosx \times \frac{d}{dx}(cosx) \\ = - 8sinx.cosx \\ = - 4sin(2x)$

Hope, this helps...