And if you were to take cross-sections of the figure, and that's what this yellow line is, if you were to take cross-sections of this figure that are vertical, that are, I should say, perpendicular to the x-axis, those cross-sections are going to be isosceles-right triangles. So this cross-section is going to look like this if you were to look at, if you were to flatten it out. So over here it's sitting, it's popping out of your page or out of your screen, but if you were to actually flatten it out, the cross-section would look like this. It's going to be an isosceles-right triangle where the hypotenuse of the isosceles-right triangle sits along the base. So it's isosceles, so that's equal to that. It's a right triangle. And then this distance between that point and this point is the same as the distance between f of x and g of x for this x value right over there.