1. Warm Up 04.25.12 Week 6

2. Section 12.1 Day 1 I will use the properties of polyhedra. Cross section The intersection of a plane slicing through a solid. The cross section is a circle.

3. Describe the cross section:Do 1:

4. Platonic Solids 5 special regular polyhedra. Don’t Write

5. Euler’s Theorem The sum of the faces (F), vertices (V), and edges (E) of a polyhedron are related by the formula: F + V = E + 2. Theorem 12.01

6. Rule 1 In a solid, each side is shared by exactly 2 polygons. 8 triangles, 6 octagons = 14 faces F + V = E + 2 14 + V = E + 2 8 (3), 6 (8) = 72 edges = 36 edges 14 + V = 36 + 2 14 + V = 38 V = 24 Ex 1

7. Ex 2 20 Hexagons 12 Pentagons x 6 x 5 edges Find the number of vertices:

8. Assign ment: Textbook Page 723, 10 – 24 all. Do 1: How many faces, edges, and vertices?