Question

How do you differentiate `f(x)=-cosx*(-2sinx)` using the product rule?

Answer 1

Find the derivative of the first term and multiply it with the second term, add that to the derivative of the second term multiplied with the first term.

Explanation:

So `dy/dx -cos(x)*-2sin(x) = (-cos(x))'(-2sin(x)) + (-cos(x))(-2sin(x))`

`= sin(x)*(-2sin(x)) + (-cos(x))(-2cos(x))`

`= -2sin^2(x) + 2cos^2(x)`