So we're only looking at this side right over here. We've now expressed this graph, this curve, as x as a function of y. So if we do it that way, what's our radius right over here? Well, our radius right over here is going to be f of y. It's going to be the square root of y. So it's going to be a function of y. I don't want to confuse you if you thought this was f of x and I'm saying this is f of y. It's going to be a function of y.