Year 8 - Maths
Securing understanding of angles from KS2
Geometrical properties: polygons
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This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
Unit Summary
In this unit pupils will investigate internal and external angles of polygons and angles made with a transveral and parallel lines. Pupils will develop their ability to formally prove properties of polygons to generalise.
Lesson Summary
You will learn to confidently state the sums of the angles around a point and on a straight line.
Key Notes
- The sum of angles at a point can be used to find missing angles.
- The angle sum of a straight line can be used to find missing angles.
- Vertically opposite angles can be used to find missing angles.
- The size of missing angles can be justified by using known facts.
Vocabulary To Learn
- Vertical angles: Vertical angles are pairs of opposite angles formed when two lines intersect at a point. They are equal.
- Vertex: A vertex is the point where two or more line segments meet. The plural is vertices.
- Similar: Two shapes are similar if the only difference between them is their size. Their side lengths are in the same proportions.
- Supplementary angles: Supplementary angles are a pair of angles that sum to 180°.
- Conjugate angles: Conjugate angles are a pair of angles that sum to 360°.
Common Mistakes To Avoid
- Angles on a straight line sum to 180°
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
The sum of angles at a point can be used to find missing angles. The angle sum of a straight line can be used to find missing angles.
2. Use this key word in a maths sentence and explain it clearly. 'Vertical angles'
Vertical angles are pairs of opposite angles formed when two lines intersect at a point. They are equal. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Angles on a straight line sum to 180°. Correction: Angles on a straight line only sum to 180° if all of those angles share a common vertex. Show two angles "on a line" at different points.
More Lessons In This Unit
- Alternate angles Study Guide
- Angles on parallel lines traversed by a straight line Study Guide
- Checking understanding of angles from KS2 Study Guide
- Co-interior angles Study Guide
- Corresponding angles Study Guide
- Deriving the sum of interior angles in multiple ways Study Guide
- Exterior angles of polygons Study Guide
- Formal angle notation Study Guide
- Formalising understanding of triangles from KS2 Study Guide
- Interior and exterior angles of regular polygons Study Guide
- Interior angles of a polygon Study Guide
- Missing angles Study Guide
- Problem solving with polygons Study Guide
- The sum of the interior angles of any triangle Study Guide
- Using the sum of the interior angles of a triangle Study Guide
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