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Similar-triangle lengths in geometric proofs topic check

Practise similar-triangle lengths in geometric proofs in G3 Additional Mathematics, check independently, and return later to review. This check covers selected skills, not the whole course topic.

Learning goals
  • Construct a geometric argument or proof
  • Find a scale factor and unknown lengths from matched sides of similar triangles
  • G3 Additional Mathematics 2027
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Similar-triangle scale factors and lengths · Check your progress

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Retention check

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Similar-triangle scale factors and lengths · Retention check

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Practise: Similar-triangle scale factors and lengths

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Revision notes

Revise geometry and reasoning

Prove congruence, similarity, circle, midpoint and tangent–chord relationships, state the conditions each step needs and test claims with counterexamples.

Key ideas

  1. Congruence, similarity and circle proofs

    Choose the triangles that contain the target, justify congruence or similarity with exact correspondences and use circle properties only in their stated configurations.

  2. Midpoint and tangent–chord proofs

    Derive midpoint relationships, distinguish alternate segments and build a non-circular proof with a missing-condition counterexample.

What the syllabus asks

From the G3 Additional Mathematics 2027 syllabus

  • Properties of parallel lines cut by a transversal, perpendicular and angle bisectors, triangles, special quadrilaterals and circles
  • Congruent and similar triangles
  • Midpoint theorem
  • Tangent-chord theorem (alternate segment theorem) (The first two properties are learnt in G3 Mathematics.)