1. Lesson 72, day 2 Pyramids and Cones

2. Pyramids Pyramid: geometric solid with a polygon base, and triangle faces (lateral faces) Vertex: top of the pyramid Lateral edges: where the lateral faces connect Axis: segment from the vertex to the center of the base Altitude: perpendicular segment from the vertex to the plane of the base

3. Pyramids Regular pyramids: base is a regular polygon and lateral faces are isosceles triangles Slant height: height of a lateral face –Only in regular pyramids

4. Cones Pyramid with a circle for a base Lateral surface: curved surface between the vertex and the base Axis: like the pyramid Altitude: like the pyramid Height of a cone and pyramid: length of the altitude

5. Volume of Pyramids and Cones

6. Example 72.4 Find the volume of the right rectangular pyramid. The height is 8 in. 7 in 9 in

7. Example 72.5 A right circular cone has a base of radius 6 ft and a height of 8 ft. Find the volume of the cone.

8. Example 72.6 Find the surface area of this regular square pyramid. Dimensions are in centimeters. 6 in 5 in

9. Surface Area of Cones Lateral surface area = π·r·l radius Slant height

10. Example 72.7 A right circular cone has a base of radius 8 m and a slant height of 10 m. Find the surface area of the right circular cone.

11. Homework P.S. 72 1-18 all, 21-26 all, 30