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Sin sqrt(x) < sqrt(sin x) for 0 < x < pi/2

Source: All-Russian Olympiad 2006 finals, problem 11.1

May 6, 2006
trigonometryfunctioncalculusderivativeinequalitiesreal analysisreal analysis unsolved

Problem Statement

Prove that sinx<sinx\sin\sqrt{x}<\sqrt{\sin x} for every real xx such that 0<x<π20<x<\frac{\pi}{2}.