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4MA1/2H Jan 2020, Question 13: Combining Circle Theorems

Pearson Edexcel International GCSE Mathematics A 4MA1 · Paper 2H (Higher) · Calculator · 4 marks

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The question, in short

Points A, B, C, D lie on a circle with centre O, AOD a diameter, angle CBD = 28° and angle BDA = 32°. Find angle BDC, justifying each step.

Summarised in our own words. Use the official paper for the exact wording and the diagram.

Solution · 4 marks

  1. 1Angle CBD = 28°, so angle CAD = 28° (angles in the same segment are equal)
  2. 2Angle ABD = 90° (angle in a semicircle is 90°)
  3. 3In triangle ABD, angle BAD = 180° − 90° − 32° = 58°
  4. 4Angle BAC = angle BAD − angle CAD = 58° − 28° = 30°
  5. 5Angle BDC = angle BAC (angles in the same segment are equal)
  6. 630

Answer30

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