1. S ECTION 1-4 P OLYGONS

2. A polygon is a closed figure in a plane, formed by connecting segments endpoint to endpoint with each segment intersecting exactly two others. Each line segment is called a side of the polygon. Each endpoint, where the sides meet, is called a vertex.

3. N AMES FOR P OLYGONS We name polygons based on the number of sides on the polygon.

4. To name a polygon, we name the vertices in order: Pentagon ABCDE Pentagon DCBAE

5. E XAMPLES OF N AMING P OLYGONS

6. A diagonal of a polygon is a line segment that connects two nonconsecutive vertices. Remember segment DE is a side of the polygon.

7. A polygon is convex if no diagonal is outside the polygon. A polygon is concave if at least one diagonal is outside the polygon.

8. Two polygons are congruent if and only if they are exactly the same size and shape. This means:

9. If quadrilateral CAMP is congruent to quadrilateral SITE, then their four pairs of corresponding angles and four pairs of corresponding sides are also congruent.

10. E XAMPLE Which polygon is congruent to ABCDE?

11. P ERIMETER The perimeter of a polygon is equal to the sum of the lengths of its sides. The perimeter of the quadrilateral is 37 cm.

12. S PECIAL P OLYGONS Equilateral Polygons

13. Equiangular Polygons

14. Regular Polygons