# Lesson Plan: Interior Angles of a Polygon Mathematics • 8th Grade

This lesson plan includes the objectives, prerequisites, and exclusions of the lesson teaching students how to find the sum of the measures of the interior angles of a polygon given the number of its sides and the measure of an angle in a regular polygon.

#### Objectives

Students will be able to

• identify and classify polygons as concave or convex,
• divide a polygon into triangles in order to find the sum of its interior angles,
• find the sum of the interior angles of a polygon given its number of sides using the formula,
• find the measure of the interior angle of a regular polygon given its number of sides using the formula,
• find the measure of an angle in an irregular polygon given its number of sides and the measure of the other angles in the polygon,
• understand the relationship between interior and exterior angles and their sums in a polygon,
• find the measure of an exterior angle of a regular polygon given its number of sides,
• find the number of sides a regular polygon has given the measure of one of its interior angles.

#### Prerequisites

Students should already be familiar with

• the sum of the angles in a triangle,
• regular and irregular polygons,
• classifying polygons by their number of sides.

#### Exclusions

Students will not cover