Tangent, Sine, and a Multiplier

Problem

Let 0<x<π20 < x < \dfrac{\pi}{2}.

1. Prove that tanx+sinx>2x\tan x + \sin x > 2x. 2. Find the largest positive integer nn such that

tanxx>n(xsinx)\tan x - x > n\,(x - \sin x)

holds for all such xx.

Answer

Solution

Difficulty7/10
Topicstrigonometry, calculus, Monotonicity, AM-GM, inequality

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