Starter quiz
- An ______ angle is an angle on the outside of a polygon between an extension of an edge and its adjacent edge.
- acute
- alternate
- exterior ✓
- interior
- obtuse
-
- Adjacent angles on a straight line sum to ______°.
- '180' ✓
The angle ° is ______°.- '70' ✓
What is the size of ∠CDA?- 73°
- 84°
- 95° ✓
- 108°
-
- A heptagon is a 7-sided polygon. The sum of its interior angles is ______°.
- '900' ✓
- Solve the equation: . ______
- '64' ✓
Exit quiz
- An interior angle and its adjacent exterior angle sum to ______°.
- '180' ✓
- In which diagram is an exterior angle marked?
The exterior angle at B is ______°.- '131' ✓
- Exterior angles in a polygon sum to ______°.
- '360' ✓
The angle ° is ______°.- '117' ✓
The value of is ______.- '96' ✓
Worksheet
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Presentation
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Lesson Details
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.
- The angle sum of a triangle can also be proven using exterior angles .
- The size of the exterior angle of any polygon can be found using the sum of angles.
Common misconception
The exterior angle is the entire reflex angle that is on the outside of each vertex of a shape.
Ask a pupil to stand and walk around the room to trace a shape. The angle that the pupil turns at each vertex is an exterior angle.
Keywords
Interior angle - an angle formed inside a polygon by two of its edges.
Exterior angle - an angle on the outside of a polygon between an extension of an edge and its adjacent edge.
Supplementary angle - a pair of angles that sum to 180°.
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