A Zero-Free Window

Problem

Let

f(x)=sin⁡2ωx2+12sin⁡ωx−12(ω>0),x∈R.f(x)=\sin^2\frac{\omega x}2+\frac 12\sin\omega x-\frac 12\qquad(\omega>0),\quad x\in\mathbb R.

Suppose f(x)f(x) has no zero in the interval (π,2π)(\pi,2\pi). Find the range of ω\omega.

Answer

Solution

Difficulty7/10
Topicstrigonometry, Trigonometric Identities, Casework

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