Question

What is the derivative of `cos (2x)`?

Answer 1

`-2sin(2x)`

Explanation:

if `y = f(g(x))`
then `y' = f'(g(x)) * g'(x)` by the chain rule, or the derivative of the outside function times the derivative of the inside function.

So the derivative of `cos(2x)` is `-sin(2x)` times the derivative of the inside, so it is `-2sin(2x)`.