1. Polygons
Section 3-1

2. Definitons Polygon Greek word meaning “many angled”
Closed plane figure formed by three or more segments (sides)
Sides can only intersect at their endpoints
The intersection of two sides is called the vertex
Name a polygon by listing the vertices in consecutive order

3. Convex and Concave Polygons
Convex (no indentation)
No segment connecting two vertices contains points outside the polygon
Concave (has indentation)
A polygon that is not convex

4. Names of Polygons Number of Sides Name of Polygon 3 Triangle 4
Quadrilateral 5
Pentagon 6
Hexagon 7
Heptagon 8
Octagon 9
Nonagon 10
Decagon 12
Duodecagon 20
Icosagon

5. Definitions Consecutive Angles Two angles with a common sideB C
<A and <B are
Consecutive angles A
<B and <C are
Consecutive angles

6. Defintions (con’t) Adjacent (consecutive) Sides Sides that intersectB C
AB and BC are
adjacent sides A

7. Defintions (con’t) Adjacent (consecutive) Vertices
Vertices of consecutive angles
Points B C
A and B are
Adjacent Vertices A

8. Defintions (con’t) Diagonal
A segment joining a pair of nonconsecutive vertices B C A
AC is a diagonal

9. Examples