Students are introduced to angles in a quadrilateral by investigating how they are formed from two triangles. More able students learn how to prove this property using algebra.

At the start of the lesson students recap finding angles in a triangle. In the main part they learn the propery of angles in a quadrilateral have a sum of 360° and how to use this to find unknown angles. The plenary challenges students to combine multiple angle properties within a single problem.

**Differentiated Learning Objectives**

- All students should be able to calculate a missing angle in a scalene quadrilateral.
- Most students should be able to calculate missing angles using the unique properties of each quadrilateral.
- Some students should be able to prove the sum of the angles in a quadrilateral.