0580/43 May/Jun 2026, Question 15: The Cosine Rule
Cambridge IGCSE Mathematics 0580 · Paper 43 (Extended) · Calculator · 3 marks
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The question, in short
Use the three given side lengths of a triangle to calculate the largest angle.
Summarised in our own words. Use the official paper for the exact wording and any diagrams.
Solution · 3 marks
- 1Largest angle is opposite 11 cm
- 2cos x = (5² + 7² − 11²)/(2 × 5 × 7) = −47/70
- 3x = cos⁻¹(−0.6714…) = 132.2°
Answer132 or 132.2 or 132.17 to 132.18
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