So once again, we could find the volume of each of these by finding the area, the cross-sectional area there, and then multiplying that times a little bit, a little dx, a little dx, which would give us 3, so this is a little dx, which would give us 3-dimensional, that's our dx, I could write that a little bit neater, dx to give us a little bit of 3-dimensional depth. So how could we, what is the volume of one of these figures going to look like? Well, if we say, let me just call this height h, and we know that h is going to be f of x minus g of x, that's this distance right over here, so let's call that h. We know that h is going to be, and maybe I should say h of x, because it is going to be a function of x, h of x is going to be f of x, f of x minus g of x, minus g of x. But given an h, what is going to be the area of this triangle? Well, this is a 45, 45, 90 triangle. If this is 90, then this is going to have to be 45 degrees, that's going to have to be 45 degrees, and we know that the sides of a 45, 45, 90 triangle are square root of 2 times the hypotenuse. So this is going to be square root of 2, sorry, square root of 2 over 2 times the hypotenuse.