Checking and securing understanding of exterior angles
Lesson details
Learning outcome
I can find the exterior angle of any regular polygon or deduce the exterior angle of an irregular polygon.
Key learning points
- The sum of the exterior angles of a polygon can be demonstrated using a point.
- The sum of the exterior angles of a polygon can be proven using interior angles and the angles on a straight line.
- An exterior and interior angles pair are supplementary.
Keywords
Polygon - A polygon is a flat (2D), closed figure made up of straight line segments.
Regular - A regular polygon has sides that are all equal and interior (inside) angles that are all equal.
Interior angle - An interior angle is an angle formed inside a polygon by two of its edges.
Exterior angle - An exterior angle is an angle on the outside of a polygon between an extension of an edge and the adjacent edge.
Common misconception
An exterior angle is equal to 360° - the size of the interior angle because angles around a point sum to 360°.
An exterior angle is an angle on the outside of a polygon between an extension of an edge and the adjacent edge.
Teacher tip
This lesson makes use of a GeoGebra activity involving commanding a turtle. Pupils would benefit from being able to access this activity and use it throughout the lesson. If this is not possible during the lesson, the link can be shared so pupils can investigate after the lesson.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.An angle is an angle formed inside a polygon by two of its edges.
Q2.Three of the interior angles of a quadrilateral are 80°, 90° and 45°. The size of the fourth interior angle is °.
Q3.The interior angles of a dodecagon (12 sides) sum to °.
Q4.Each interior angle of a regular octagon is °.
Q5.A regular polygon has interior angles of size 162°. The polygon has sides.
Q6.Which interior angles are possible in a regular polygon?
Assessment exit quiz
6 Questions
Q1.An angle is an angle on the outside of a polygon between an extension of an edge and the adjacent edge.
Q2.The exterior angles of any polygon sum to °.
Q3.An interior angle and its adjacent exterior angle sum to °.
Q4.The size of each exterior angle of a regular pentagon is °.
Q5.A regular polygon has exterior angles of 40°. The polygon has sides.
Q6.Which of these exterior angles are possible for a regular polygon?
To help you plan your 10 maths lesson on: Checking and securing understanding of exterior angles, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 10 maths lesson on: Checking and securing understanding of exterior angles, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 4 maths lessons from the Angles unit, dive into the full secondary maths curriculum, or learn more about lesson planning.