Year 8 - Maths
Formalising understanding of triangles 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 classify triangles and know their relevant properties.
Key Notes
- An equilateral triangle is a regular triangle and has particular properties.
- A scalene triangle has specific properties.
- An isosceles triangle has properties including a line of symmetry that splits it into two congruent triangles.
- A right-angled triangle can be scalene or isosceles.
Vocabulary To Learn
- Equilateral: Equilateral triangles have three equal-sized angles and three edges of equal length. They are regular triangles.
- Scalene: Scalene triangles have three different-sized angles and three different-sized edges (sides).
- Isosceles: Isosceles triangles have two equal-sized angles and two sides of the same length.
- Right-angled triangle: A right-angled triangle has exactly one 90° interior angle.
Common Mistakes To Avoid
- The horizontal side length of an isosceles triangle is always the base side.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
An equilateral triangle is a regular triangle and has particular properties. A scalene triangle has specific properties.
2. Use this key word in a maths sentence and explain it clearly. 'Equilateral'
Equilateral triangles have three equal-sized angles and three edges of equal length. They are regular triangles. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: The horizontal side length of an isosceles triangle is always the base side. Correction: The base side of an isosceles triangle can have any orientation. It is important to look at the hash marks, angle markers, or measurements.
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
- 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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