Question

Solve for $x$:

$2\cos 3x-1=0$

Answer 1

Given, $2\cos 3x-1=0$

$\Rightarrow \cos 3x=\frac{1}{2}$

$\Rightarrow \cos 3x=\cos {60}^o[\because \cos {60}^o=\frac{1}{2}]$

$\Rightarrow 3x={60}^o$

$\Rightarrow x={20}^o$

Hence, the $x={20}^o$ is the solution of the given equation.