Exterior angles of polygons

A complete lesson on exterior angles of polygons. I cover exterior angles after interior angles, so I should point out that the starter does rely on pupils knowing how to do calculations involving interior angles. See my other resources for a lesson on interior angles.

Activities included:

Starter:
Some recap questions involving interior angles and also exterior angles, but with the intention that pupils just use the rule for angles on a line, rather than a formal definition of exterior angles (yet).

Main:

• A “what’s the same,what’s different” prompt followed by examples and non-examples of exterior angles, to get pupils thinking about a definition of them.
• A mini- investigation into exterior angles.
• Prompts to establish and then prove algebraically that exterior angles sum to 360 degrees for a triangle and a quadrilateral. The proofs could be skipped, if you felt this was too hard.
• A worksheet of more standard exterior angle questions with a progression in difficulty.

Plenary:
A slide animating a visual proof of the rule, followed by a hyperlink to a different visual proof.

Printable worksheets and answers included. I’ve also included suggested questions and extensions in the notes boxes at the bottom of each slide.

Please review if you buy as any feedback is appreciated!