4PM1/01R Jan 2023, Question 2: The Ambiguous Case of the Sine Rule
Pearson Edexcel International GCSE Further Pure Mathematics 4PM1 · Paper 1R · Calculator · 3 marks
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The question, in short
In triangle ABC with angle BAC = 50°, AB = 10 cm and BC = 9 cm, find the two possible values of angle BCA = x°, to one decimal place.
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Solution · 3 marks
- 1Sine rule: sin BCA/10 = sin 50°/9
- 2sin BCA = 10 sin 50°/9 = 0.8512…
- 3BCA = 58.338…° = 58.3°
- 4or BCA = 180° − 58.338…° = 121.7°
Answerx = 58.3 or x = 121.7
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