MathDB

3

Part of 2011 Singapore Senior Math Olympiad

Problems(1)

Trigonometric equality

Source: Singapore MO 2011 senior round 2 Q3

6/25/2011
Find all positive integers nn such that cos⁡πncos⁡2πncos⁡3πn=1n+1\cos\frac{\pi}{n}\cos\frac{2\pi}{n}\cos\frac{3\pi}{n}=\frac{1}{n+1}
trigonometryalgebra proposedalgebra