Geometry — Interior and Exterior Angles of Polygons

About this lesson

This unit teaches geometry concepts related to polygons, specifically focusing on convex polygons. It covers the formula for calculating the sum of interior angles, which is (n-2) x 180°, and explains that the sum of exterior angles (one at each vertex) is always 360°. It also provides formulas for finding the measure of an interior angle of a regular polygon and the number of diagonals in a convex polygon. The unit includes worked examples, self-evaluation questions, and exercises that apply these formulas to find unknown angles, numbers of sides, and numbers of diagonals. Real-life contexts include an octagon-shaped building, a carpenter making a locker to fit a corner, and arranging tables in a conference hall. By the end, a student should be able to calculate sums of interior and exterior angles, determine measures of angles in regular polygons, find the number of sides given angle measures, and compute the number of diagonals for a given polygon.