4MA1/1F Jan 2022, Question 18: Choosing the Right Trigonometric Ratio
Pearson Edexcel International GCSE Mathematics A 4MA1 · Paper 1F (Foundation) · Calculator · 3 marks
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The question, in short
Using a right-angled triangle ABC with AC = 8.4 cm and angle ACB = 65°, calculate side AB to 3 significant figures.
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Solution · 3 marks
- 1The triangle is right-angled and the 8.4 cm side is the hypotenuse.
- 2AB is the side opposite the 65° angle.
- 3sin 65° = AB ÷ 8.4
- 4AB = 8.4 × sin 65°
- 5AB = 8.4 × 0.9063 = 7.613
- 6AB = 7.61 cm (3 s.f.)
Answer7.61
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