Instead of having an x up here, our upper bound is a sine of x. So one way to think about it is if we were to define g of x as being equal to sine of x, equal to sine of x, our capital F of x can be expressed as capital F of x is the same thing as h of, h of, instead of an x, everywhere we see an x, we're replacing it with a sine of x. So it's h of g of x, g of x. You can see the g of x right over there. So you replace x with g of x for where in this expression, you get h of g of x, and that is capital F of x. Now why am I doing all of that? Well, this might start making you think about the chain rule, because if this is true, then that means that capital F prime of x is going to be equal to h prime of g of x, h prime of g of x, times g prime of x.