1. Polygons and Angles Lesson #3 Pg. 27

2. Key Vocabulary Polygon – A simple, closed figure formed by three or more line segments Equilateral – A polygon in which all the sides are congruent Equiangular – A polygon in which all the angles are congruent Regular Polygon – A polygon that is both, equilateral and equiangular

3. Polygons you Should KNOW.. Number of SidesName of Polygon 3Triangle 4Quadrilateral 5Pentagon 6Hexagon 7Heptagon 8Octagon 9Nonagon 10Decagon 11Hendecagon 12Dodecagon

4. Interior Angle Sum of a Polygon The sum (S) of the measures of the interior angles of a polygon is (n – 2) 180, where n represents the number of sides in the polygon HINT: A triangle has 180° in interior angles, from one vertex in the polygon connect line segments to the other vertices to see how many triangles are created. Multiply the amount of triangles by 180

5. Examples of Interior Angles in Polygons Number of Sides (n) Sketch of Figure Number of Triangles Sum of Angle Measure (n-2)180 311(180°)=180° 4 5 6

6. Examples Find the sum of the measures of the interior angles of a decagon. Hexagon? Octagon? 15-gon?

7. Examples Each chamber of a bee honeycomb is a regular hexagon. Find the measure of an interior angle (1) of a regular hexagon. Octagon? Heptagon? 20-gon?

8. Exterior Angles of a Polygon In a polygon, the sum of the measures of the exterior angles, one at each vertex, is 360°. 1 2 3 4 5 5 1 2 3 4

9. Examples Find the measure of an exterior angle in a regular hexagon. Triangle? Quadrilateral? Octagon?

10. Homework HC: pg. 31-32 (1-15) CC: pg. 31-32 (1-7, 9, 11, 14, 15)