Question
Find the general solution of the equation $4 \cos ^2 x=1$.

Answer

Given:
$4 \cos ^2 x=1$
$\cos ^2 x=\frac{1}{4}$
$\cos ^2 x=\cos ^2\left(\frac{\pi}{3}\right)$
$\left[\right.$ Using $\left.\cos ^2 x=\cos ^2 \alpha \Rightarrow x=n \pi \pm \alpha\right]$
$x=n \pi \pm \frac{\pi}{3}$ where $n \in Z$

 

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