 So in 13.1 we talked about volume of prisms and cylinders. In 13.2 we're going to talk about volume of pyramids and cones. You'll notice that the volume formula is already written here for you, and you'll notice also that it looks very similar to prisms and cylinders, difference being that the volume is one-third times the area of the base times the height. So there's a couple things we have to talk about before we move into doing the examples. Notice here it says that there's a height which is also referred to as an altitude of the pyramid or cone. And that is the segment that's drawn from the vertex of the pyramid and perpendicular to the base. So on this cone this right here would be the height or the altitude of the cone. Similar, if I look to the pyramid that's here, if I was going to draw the height of the pyramid it would be perpendicular to the base. So this would be a 90 degree angle and this would be the height of the pyramid. There's another height that's going to come into play when you're dealing with pyramids or cones, and that is something that we refer to as this italic L. And that is the slant height of the pyramid or cone. What it is, it's actually the height of the lateral face. What we mean by that is if you look at the lateral face of a pyramid, I'm going to just change colors here. So this pyramid has a triangular lateral face. And L, the slant height, would be the height of that pyramid. Over here on the cone it's a lot easier. The slant height is the edge of the cone. So when we are looking at pyramids and cones, the volume formula, again, very similar to cylinders and prisms, it just has a 1 third multiplied by the area of the base then times the height of the pyramid or cone. So let's look at some examples. So here we have a square pyramid. We're going to go through step by step and find the volume of this pyramid. Now because they tell us it's a square pyramid, we know that all four sides of the base are congruent. So CD, DF, FB and BC should all be equal to four. The height of this pyramid is the segment that is perpendicular to the base. So six is the height of this pyramid. And I will just go ahead and do that. Height is six. And the area of the base is going to be base times height. But because this is a square, four times four is sixteen. Again, the base is this square. And so we have four times four to get the area of that base. The height of the pyramid, remember we already discovered that is six. And so to find the volume of this pyramid, we are going to take one-third times the area of the base times the height of the pyramid. So that's going to be one-third times sixteen times six. Now when you enter this in your calculator, it's much easier to do sixteen times six and then divide by three. And when you do that, you should get thirty-two cubic units. Again remember that volume is always units cubed. So we use a exponent of three when we write the unit. We do the same thing when we're working with the cone. So here the height of the cone would be seven. So I'm just going to draw a little arrow here. That is the height of the cone. And then the area of the base, well because a cone has a base that is a circle, we're going to do pi r squared. The circle that radius is three. So pi times three squared would be nine pi. We said that the height of the cone is seven. So when we find the volume of the cone, it's going to be one-third times the area of the base times the height of the cone. So in this case, the area of the base, remember we found was nine pi. And the height of the cone is seven. So if you multiply nine times seven, you get sixty-three. Divide that by three, you get twenty-one pi. And that would be cubic units.