 In this video, formula for surface area of cones, we're just going to identify a few pieces of cones and then quickly give you the formula for the lateral area and the surface area. So we're just going to identify the following four pieces. The base of the cone, just like the base of a cylinder, is a circle. And in this case, we can name it because we do have a center for that circle. We're going to call this circle K. And in our formulas, we identify the base as a capital B. The radius, of course, is going to be this segment right here, segment KM in this case. And that symbol for the radius is lowercase R. And then for number three and four, these are the two values that a lot of people get mixed up. So you want to make sure that you have these down. The height or the altitude of the cone is that vertical distance that goes from the top vertex or the apex of the cone and is perpendicular to the center of the base, the center of that circle. Sometimes you hear it referred to as height. Sometimes you hear it referred to as altitude. In this case, it's represented by segment JK. And that vertical height is always going to be represented by a lowercase H. And then the slant height is what gets mixed up with the altitude sometimes. The slant height, as you could guess, is the slanty piece. And just remember, we're going to be needing to use the Pythagorean theorem sometimes to figure out the altitude of the slant height because it does create that right triangle. So the segment that represents the slant height in this case would be JM. And remember, the slant height is always that curse of lowercase L. And so let's talk about what you're going to need to know for the formulas for surface area of a cone. This right here is what we used for the surface area of a pyramid. And pyramids are similar to cones as they both have one base. So their formulas are going to be similar. But just as we did for prisms versus cylinders, we're going to change a few things because now we have that circle for a base. So we're going to replace the P. The perimeter of the base is now going to be 2 pi r because that's the circumference or the perimeter of that circle. And so when we plug that in to our formula that we used for the pyramid, these twos are going to cancel out and I'm just left with the pi and the r. So pi r times L becomes the lateral area of that cone. And then my base, my B in the formula is replaced by the area of my base in the area of the circle of course is pi r squared. And so what you need to write down in your formula books, on your formula flip book or notes or wherever you're keeping that, the surface area, total surface area of a cone, pi rL plus pi r squared with r being the radius of the base and L being the slant height of the cone. Those are the only two values you'll need when you're calculating surface area of cones. And then of course if we're talking about just the lateral area of a cone, we're going to take off that area of the base and actually this should be changed to L a for latitude or lateral area. Lateral area of the cone then becomes just the pi rL that represents the area of the lateral area of that cone. And that's all you need to know for this video.