Vertically opposite angles

A complete lesson on vertically opposite angles. Does incorporate problems involving the interior angle sum of triangles and quadrilaterals too, to make it more challenging and varied (see cover image for an idea of some of the easier problems)

Activities included:

Starter:
A set of basic questions to check if pupils know the rules for angles at a point, on a line, in a triangle and in a quadrilateral.

Main:

• A prompt for pupils to reflect on known facts about angles at the intersection of two lines, naturally leading to a quick proof that vertically opposite angles are equal.
• Some subtle non-examples/discussion points to ensure pupils can correctly identify vertically opposite angles.
• Examples and a set of questions for pupils to consolidate. These start with questions like the cover image, then some slightly tougher problems involving isosceles triangles, and finally some tricky and surprising puzzles.
• A more investigatory task, a sort-of angle chase where pupils need to work out when the starting angle leads to an integer final angle.

Plenary:
An animation that shows a dynamic proof that the interior angle sum of a triangle is 180 degrees, using the property of vertically opposite angles being equal.

Printable worksheets and answers included.

Please do review if you buy, as any feedback is helpful!