Year 10 - Maths
Checking and securing understanding of congruent triangles (ASA)
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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 investigate the effect of an enlargement on the perimeter and area of a 2-D shape and the volume of a 3-D shape.
Lesson Summary
You will learn to understand and use the criteria by which triangles are congruent (ASA).
Key Notes
- By knowing two angles and the length between them in the triangle and image, you can prove congruence.
- The angle pairs must be identical.
- This rule is derived from the SAS criteria for congruence.
Vocabulary To Learn
- Congruent: If one shape can fit exactly on top of another using rotation, reflection or translation, then the shapes are congruent.
- Similar: Two shapes are similar if the only difference between them is their size. Their side lengths are in the same proportions.
Common Mistakes To Avoid
- Pupils may struggle to spot congruent triangles when the two angles are not at the ends of the known side.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
By knowing two angles and the length between them in the triangle and image, you can prove congruence. The angle pairs must be identical.
2. Use this key word in a maths sentence and explain it clearly. 'Congruent'
If one shape can fit exactly on top of another using rotation, reflection or translation, then the shapes are congruent. 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 to spot congruent triangles when the two angles are not at the ends of the known side. Correction: Encourage pupils to add any further information to diagrams, like the third angle, before starting to prove congruence.
More Lessons In This Unit
- Checking and securing understanding of congruent triangles (RHS) Study Guide
- Checking and securing understanding of congruent triangles (SAS) Study Guide
- Checking and securing understanding of congruent triangles (SSS) Study Guide
- Checking and securing understanding of direct proportion in context Study Guide
- Problem solving with advanced similarity knowledge Study Guide
- Problem solving with similarity Study Guide
- The effect of enlargement on the area of a shape Study Guide
- The effect of enlargement on the perimeter of a shape Study Guide
- The effect of enlargement on the volume of a 3D shape Study Guide
- Using the scale factor for enlarging a volume Study Guide
- Using the scale factor for enlarging an area Study Guide
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