Year 8 - Maths
Problem solving with polygons
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 your knowledge of polygons to solve problems.
Key Notes
- Problems can be solved using parallel line angle facts.
- Problems can be solved using interior and exterior angles of polygons.
- Problems can be solved and the solution justified using angle facts.
- It is possible to write algebraic statements about connected angles.
- Your knowledge of algebraic manipulation may be useful.
Vocabulary To Learn
- Corresponding angles: Corresponding angles are a pair of angles at different vertices on the same side of a transversal in equivalent positions.
- 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.
- Co-interior angles: Co-interior angles are on the same side of the transversal line and in between the two other lines.
- Interior angles: An interior angle is an angle formed inside a polygon by two of its edges.
- Exterior angles: An exterior angle is an angle on the outside of a polygon between an extension of an edge and its adjacent edge.
Common Mistakes To Avoid
- Pupils might not know how to start an angle problem if they focus too much on the final solution.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
Problems can be solved using parallel line angle facts. Problems can be solved using interior and exterior angles of polygons.
2. Use this key word in a maths sentence and explain it clearly. 'Corresponding angles'
Corresponding angles are a pair of angles at different vertices on the same side of a transversal in equivalent positions. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Pupils might not know how to start an angle problem if they focus too much on the final solution. Correction: You can start an angle problem by working out any angle on the diagram. The more angles you work out, the easier the final solution becomes.
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
- 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.