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cosa+cosb+cosc>sina+sinb+sinc- All-Russian MO 2004 Regional (R4) 10.1

Source:

September 27, 2024
trigonometryalgebrainequalities

Problem Statement

The sum of positive numbers a,b,ca, b, c is equal to π/2\pi/2. Prove that cosa+cosb+cosc>sina+sinb+sinc.\cos a + \cos b + \cos c > \sin a + \sin b + \sin c.