1. Geometry: Part 2
3-D figures

2. Polyhedron 3-dimensional analog of a polygon
Closed surface made up of polygons
Any 2 polygons may have only one shared edge
Vertex
Edge
Face

3. Prism Polyhedron with 2 opposite faces that are identical polygons
Faces are called bases
Bases are joined by lateral faces
If the lateral face is a rectangle it is a right prism

4. Examples: 2 hexagons for bases Right Hexagonal prism
2 rectangles for bases
Right rectangular prism
base
Lateral face

5. Geometry in the Real World

6. Pyramid
Base is any regular polygon
All sides are triangles

7. Platonic Solids All sides are equal All angles are the same
All faces are identical
Same number of polygons meet at each vertex
Only five solids meet these criteria: Platonic solids

8. Tetrahedron Composed of 4 equilateral triangles
3 triangles meet at vertex
Represented fire to the ancient Greeks

9. Hexahedron (Cube) Composed of 6 squares 3 squares meet at a vertex
Represented the stable earth

10. Octahedron Composed of 8 equilateral triangles
4 triangles meet at a vertex
Represented air

11. Dodecahedron Composed of 12 equilateral pentagons
3 pentagons meet at a vertex
Represented the 12 signs of the Zodiac

12. Icosahedron Composed of 20 equilateral triangles
5 triangles meet at a vertex
Represented water

13. Models of Polyhedra