4MA1/1H Jan 2019, Question 10: Choosing the Right Trigonometric Ratio
Pearson Edexcel International GCSE Mathematics A 4MA1 · Paper 1H (Higher) · Calculator · 5 marks
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The question, in short
Right-angled triangle with a point C on one side: from a 13 cm side, an 8 cm length and a 20° angle, find angle BAC to 1 decimal place.
Summarised in our own words. Use the official paper for the exact wording and the diagram.
Solution · 5 marks
- 1Triangle ACD: CD = 13 × tan 20° = 4.7316…
- 2BD = BC + CD = 8 + 4.7316… = 12.7316…
- 3Triangle ABD: tan BAD = 12.7316… ÷ 13, so angle BAD = 44.402…°
- 4Angle BAC = 44.402… − 20 = 24.402…
- 5= 24.4 (1 d.p.)
Answer24.4
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