So f prime of x is equal to, so for x is less than zero, we're going to take the derivative of this first case. So the derivative of one is just zero. The derivative of negative two sine of x, well derivative of sine of x is just cosine of x. So it's going to be negative two cosine of x. Negative two cosine of x for x is less than zero. And then for x is greater than zero, I'll do this in another color, I'll do it in orange. We have this case right over here.