Polygons

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

2. Polygons • A polygon is named based on the number of sides it has • triangle, quadrilateral, pentagon, hexagon, heptagon, octagon, nonagon, decagon, undecagon, dodecagon • A polygon with more than 12 sides is an n-gon, e.g., a 20-gon • A polygon is named by listing the vertices in order • Consecutive edges, vertices, and angles are the edges, vertices, and angles next to each other

3. Polygons • A diagonal of a polygon is a line segment that connects two nonconsecutive vertices • A polygon is convex if no diagonal lies outside the polygon • A polygon is concave if at least one diagonal lies outside the polygon

4. Polygons • Congruent polygons • Two polygons are congruent if and only if the corresponding sides and angles are congruent • Using “if and only if” means the statement is true in both directions • If two polygons are congruent then the corresponding sides and angles are congruent • If the corresponding sides and angles of two polygons are congruent then the polygons are congruent CAMP  SITE

5. Polygons • Special polygons • Equilateral polygons have all sides congruent • Equiangular polygons have all angles congruent • Regular polygons are both equilateral and equiangular (All sides and all angles are congruent)