#### Objectives

- Determine that the interior angle of a polygon and an exterior angle of a polygon form a linear pair (i.e., the 2 angles are supplementary)
- Determine that if one exterior angle is drawn at each vertex of a convex polygon, then the sum of the measures of those exterior angles is 360°
- Determine a formula for the measure of one exterior angle of a regular polygon and use this to discover an alternative form for the formula that is typically used to calculate the measure of the interior angle of a regular polygon

#### Vocabulary

- exterior angle of a polygon
- regular polygon
- irregular polygon
- interior angle of a polygon

#### About the Lesson

This lesson involves moving an arrow along the side of regular and irregular polygons to form an exterior angle with the adjacent side of the polygon. As a result, students will:

- Discover that an interior and exterior angle of a polygon form a linear pair.
- Determine that the sum of the measures of the exterior angles of any convex polygon is 360°.