4MA1/2F Jun 2023, Question 28: Choosing the Right Trigonometric Ratio
Pearson Edexcel International GCSE Mathematics A 4MA1 · Paper 2F (Foundation) · Calculator · 4 marks
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The question, in short
In right-angled triangle ABD with AB = 14 cm and AD = 8 cm, point C lies on BD so that angle BAC = 38°. Find CD to 3 significant figures.
Summarised in our own words. Use the official paper for the exact wording and the diagram.
Solution · 4 marks
- 1BD = √(14² − 8²) = √(196 − 64) = √132 = 11.489...
- 2angle BAD = cos⁻¹(8/14) = cos⁻¹(0.5714) = 55.15°
- 3angle CAD = 55.15° − 38° = 17.15°
- 4tan(17.15°) = CD / 8
- 5CD = 8 × tan(17.15°) = 8 × 0.3088 = 2.47
Answer2.47
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