Well, instead of thinking about the area of each of these rectangles, what happens if we rotate each of these rectangles around the x-axis? So let's do it. So let's take each of these. Let's say you have this dx right over here, and you rotate it around the x-axis. So if you were to rotate this thing around the x-axis, so I'm trying my best to, around the x-axis, you rotate it, what do you end up with? What do you end up with? Well, you get something that looks kind of like a coin, like a disk, like a quarter of some kind.