Now the left-hand side is pretty straightforward. The derivative with respect to x of g of x, that's just going to be g prime of x. But what is the right-hand side going to be equal to? Well, that's where the second fundamental theorem of calculus is useful. I'll write it right over here. Second fundamental, I'll abbreviate a little bit, theorem, theorem of calculus. It tells us, let's say we have some function capital F of x, and it's equal to the definite integral from a, some constant a to x of lowercase f of t dt.