0580/23 May/Jun 2021, Question 23: The Cosine Rule
Cambridge IGCSE Mathematics 0580 · Paper 23 (Extended) · Calculator · 4 marks
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The question, in short
Given a triangle with sides 11 cm, 10 cm and 9 cm, work out the size of its biggest angle.
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Solution · 4 marks
- 1Largest angle is opposite the longest side, 11 cm
- 2cos θ = (10² + 9² − 11²)/(2 × 10 × 9)
- 3= 60/180 = 1/3
- 4θ = 70.5°
Answer70.5 or 70.52 to 70.53
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