Year 8 - Maths
Constructing triangles
Constructions
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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 we develop skills in using a pair of compasses and ruler to construct various accurate shapes and angles including triangles, rhombi, perpendicular lines and angle bisectors.
Lesson Summary
You will learn to use intersecting circles to construct triangles from given lengths.
Key Notes
- A construction is an accurate drawing made using geometrical properties.
- A scalene triangle can be constructed using intersecting circles with different radii.
- An equilateral triangle can be constructed using intersecting circles with equal radii.
- An isosceles triangle can be constructed using intersecting circles.
Vocabulary To Learn
- Scalene triangle: Scalene triangles have three different-sized angles and three edges of different lengths.
- Isosceles triangle: Isosceles triangles have two equal-sized angles. Two of the edges are equal in length.
- Equilateral triangle: Equilateral triangles have three equal-sized angles and three edges of equal length. They are regular triangles.
- Radius: The radius is any line segment that joins the centre of a circle to any point on its circumference.
Common Mistakes To Avoid
- Pupils may avoid using the pair of compasses and opt for a ruler instead.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
A construction is an accurate drawing made using geometrical properties. A scalene triangle can be constructed using intersecting circles with different radii.
2. Use this key word in a maths sentence and explain it clearly. 'Scalene triangle'
Scalene triangles have three different-sized angles and three edges of different lengths. 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 avoid using the pair of compasses and opt for a ruler instead. Correction: Emphasise the efficiency and accuracy of using compasses instead of a ruler in the construction of their triangles.
More Lessons In This Unit
- Bisecting an angle Study Guide
- Checking compass skills Study Guide
- Constructing rhombi Study Guide
- Diagonals of a rhombus Study Guide
- Perpendicular bisector of a line segment Study Guide
- Perpendicular to a given line through a given point Study Guide
- Problem solving with constructions Study Guide
- Securing the skill of using a pair of compasses Study Guide
- Understanding constructing a circle Study Guide
Browse all guides in the Year 8 Maths guide library.