Polygon Interior Angle Sum | Finding Missing Angles in Geometry

In this Geometry lesson, we learn how to find the *sum of the interior angles of polygons* by dividing polygons into triangles and discovering a pattern. We'll explore triangles, quadrilaterals, pentagons, hexagons, and other polygons to understand where the Interior Angle Sum Formula comes from. *After watching this lesson, you should be able to:* Identify polygons by their number of sides. Divide a polygon into triangles using diagonals from one vertex. Determine the number of triangles formed inside a polygon. Explain why the sum of interior angles depends on the number of sides. Use the Polygon Interior Angle Sum Formula. Find the measure of each interior angle of a regular polygon. Solve problems involving missing interior angles. *Key Vocabulary:* Polygon • Interior Angle • Diagonal • Triangle • Quadrilateral • Pentagon • Hexagon • Regular Polygon • Interior Angle Sum *Important Formulas:* Sum of Interior Angles: S = (n − 2) × 180° where n represents the number of sides. Each Interior Angle of a Regular Polygon: A = [(n − 2) × 180°] ÷ n *Remember:* A polygon with n sides can be divided into (n − 2) triangles by drawing diagonals from one vertex. 📓 *While Watching:* WATCH → WRITE → TRY → QUESTION 1. Complete the notes and examples in your Geometry notebook. 2. Pay attention to the pattern between the number of sides and the number of triangles. 3. Pause the video and try each example before watching the solution. 4. Be prepared to explain why the formula contains (n − 2). Come to class ready to apply polygon angle relationships to more challenging problems!