If $2 \sin \left(\theta+\frac{\pi}{3}\right)=\cos \left(\theta-\frac{\pi}{6}\right)$, then $\tan \theta$

If $2 \sin \left(\theta+\frac{\pi}{3}\right)=\cos \left(\theta-\frac{\pi}{6}\right)$, then $\tan \theta$
  1. $\frac{-1}{\sqrt{3}}$
  2. $-\sqrt{3}$
  3. $\sqrt{3}$
  4. $\frac{1}{\sqrt{3}}$

Solution

$\begin{aligned} & 2 \sin \left(\theta+\frac{\pi}{3}\right)=\cos \left(\theta-\frac{\pi}{6}\right) \\ & 2\left[\sin \theta \cos \frac{\pi}{3}+\cos \theta \sin \frac{\pi}{3}\right]=\left(\cos \theta \cos \frac{\pi}{6}+\sin \theta \sin \frac{\pi}{6}\right) \\ & \therefore 2\left(\frac{\sin \theta}{2}+\frac{\sqrt{3} \cos \theta}{2}\right)=\left(\frac{\sqrt{3} \cos \theta}{2}+\frac{\sin \theta}{2}\right) \\ & \therefore\left(\frac{\sin \theta}{2}+\frac{\sqrt{3} \cos \theta}{2}\right)=0 \Rightarrow \sin \theta+\sqrt{3} \cos \theta=0 \Rightarrow \tan \theta=-\sqrt{3} \end{aligned}$

Asked in: MHT CET 2021 (21 Sep Shift 1)

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