Year 8 - Maths
Diagonals of a rhombus
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 appreciate that the diagonals of a rhombus bisect one another at right angles and the angles are bisected.
Key Notes
- An isosceles triangle has a line of symmetry that splits it into two congruent triangles.
- In a rhombus each diagonal splits the rhombus into two congruent isosceles triangles bisecting the angles.
- The two diagonals meet at right angles.
- The two diagonals bisect each other.
Vocabulary To Learn
- Bisect: To bisect means to cut or divide an object into two equal parts.
- Altitude: The altitude of a triangle is a line segment from a vertex of a triangle to the opposite edge. It is perpendicular to that edge.
Common Mistakes To Avoid
- Pupils may struggle with a diagonal of a shape being vertical or horizontal.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
An isosceles triangle has a line of symmetry that splits it into two congruent triangles. In a rhombus each diagonal splits the rhombus into two congruent isosceles triangles bisecting the angles.
2. Use this key word in a maths sentence and explain it clearly. 'Bisect'
To bisect means to cut or divide an object into two equal parts. 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 a diagonal of a shape being vertical or horizontal. Correction: By reminding pupils of the definition, ask them to check if it fits and the shape could be rotated as well.
More Lessons In This Unit
- Bisecting an angle Study Guide
- Checking compass skills Study Guide
- Constructing rhombi Study Guide
- Constructing triangles 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.