And the point is to really show you where that formula that you might see in a calculus book actually comes from, that it just comes from the exact same principles that we did in the last video. It's not for you to memorize that formula. I highly recommend against that because then you really won't know what's going on. It's really just to do it, it's better to do it from first principles where you find the volume of each of these disks and think of it that way. But let's just generalize what we saw in the last video. So instead of saying that this is y is equal to x squared, let's say that this is the graph, this function right over here, this function right over here, let's just generalize it and call it y is equal to f of x. And instead of saying we're going between 0 and 2, let's just say we're going between a and b.