Interior angles of polygons

A complete lesson on interior angles of polygons.

Activities included:

Starter:
A slide showing examples and non-examples of interior angles, for pupils to think about a definition, followed by a set of images where pupils must identify any interior angles (sounds easy and dull, but isn’t!)

Main:

• A recap of visual proofs of why the interior angles of a triangle sum to 180 degrees and those of a quadrilateral sum to 360 degrees, leading to the obvious question of “what next?”
• Prompts for the usual “investigation” into the sum of interior angles for polygons, by splitting into triangles.
• A set of questions designed to be done with mini whiteboards, starting with basic sums of interior angles, interior angles of regular polygons and finally a few variations (see cover image).
• A four-part worksheet (one page if printed two-a-side and two-sided) with a similar progression in difficulty.

Plenary:
A slide summarising the rules encountered, together with some key questions to check for any misconceptions.

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!