Year 8 - Maths
Angles on parallel lines traversed by a straight line
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 use facts about a pair of parallel lines traversed by a straight line.
Key Notes
- Alternate, corresponding and co-interior angles can be identified in diagrams containing pairs of parallel lines.
- Facts about angles in parallel lines can be used to find unknown angles.
- Facts about angles in parallel lines can be used in succession to find multiple unknown angles.
Vocabulary To Learn
- Parallel: Two lines are parallel if they are straight lines that are always the same (non-zero) distance apart.
- 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.
- Corresponding angles: Corresponding angles are a pair of angles at different vertices on the same side of a transversal in equivalent positions.
- Co-interior angles: o-interior angles are on the same side of the transversal line and in between the two other lines.
- Vertically opposite angles: Vertical angles are pairs of opposite angles formed when two lines intersect at a point. They are equal.
Common Mistakes To Avoid
- Pupils may struggle with the justifications rather than getting to the answer.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
Alternate, corresponding and co-interior angles can be identified in diagrams containing pairs of parallel lines. Facts about angles in parallel lines can be used to find unknown angles.
2. Use this key word in a maths sentence and explain it clearly. 'Parallel'
Two lines are parallel if they are straight lines that are always the same (non-zero) distance apart. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Pupils may struggle with the justifications rather than getting to the answer. Correction: Keep asking pupils "why?" and encourage them to ask themselves, whenever they are working out an angle.
More Lessons In This Unit
- Alternate angles 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
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