The Triangle Trick

Here's a secret: EVERY polygon can be split into triangles by drawing lines from one vertex. A quadrilateral splits into 2 triangles, a pentagon into 3, a hexagon into 4... Since each triangle has 180°, you can calculate the interior angles of ANY polygon!

Visual: Polygon Interior Angles

Pattern: triangles = n − 2, each triangle = 180°

This introduction covers The Triangle Trick within Angles in Polygons for GCSE Mathematics. Revise Angles in Polygons in Geometry & Measures for GCSE Mathematics with 12 exam-style questions and 3 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 1 of 10 in this topic. Use this introduction to connect the idea to the wider topic before moving on to questions and flashcards.