Year 8 - Maths
Alternate angles
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 recognise that a pair of parallel lines traversed by a straight line produces equal alternate angles.
Key Notes
- Alternate angles can be identified in an arrangement of 3 line segments.
- If two of the lines are parallel these alternate angles are equal.
- Knowledge of alternate angles can be used to find unknown angles.
- Knowledge of corresponding and alternate angles can be used to find unknown angles.
Vocabulary To Learn
- Alternate angles: A pair of angles both between or both outside two line segments that are on opposite sides of the transversal that cuts them.
Common Mistakes To Avoid
- Referring to alternate angles as 'Z' angles because of the arrangement of the lines.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
Alternate angles can be identified in an arrangement of 3 line segments. If two of the lines are parallel these alternate angles are equal.
2. Use this key word in a maths sentence and explain it clearly. 'Alternate angles'
A pair of angles both between or both outside two line segments that are on opposite sides of the transversal that cuts them. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Referring to alternate angles as 'Z' angles because of the arrangement of the lines. Correction: Modelling the justification correctly through every example and using exterior alternate angles to highlight the limitations of 'Z' angles.
More Lessons In This Unit
- 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
- Securing understanding of angles from KS2 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
Browse all guides in the Year 8 Maths guide library.