Discovering the Sum of Interior Angles Through Polygon Triangulation
Use the Interactive Polygon Simulator to form triangles, identify patterns and explain why the interior-angle formula works.
Guiding Question
How can we determine the sum of the interior angles of a polygon without measuring every angle separately?
Learning Objectives
By the end of the activity, students should be able to:
- Triangulate a regular polygon from one vertex.
- Derive the interior-angle-sum rule using the 180° angle sum of a triangle.
- Calculate the sum of the interior angles of any given regular polygon using the derived rule.
Activity Resources
Select a resource below to begin or support the activity.
Interactive Polygon Simulator
Form triangles, compare polygons and identify patterns using the interactive simulator.
Use SimulatorStudent Investigation Worksheet
Record your predictions, observations, calculations and mathematical conclusions.
Open WorksheetActivity Plan
View the objectives, materials, teaching sequence and references for the activity.
Open Activity Plan