Question

If $cos3\theta =\frac{\sqrt{3}}{2}$;
$0^{\circ }<\theta <{20}^{\circ }$ , then value of $\theta$ is:

• A. 15 degrees
• B. 10 degrees
• C. 0 degrees
• D. 12 degrees

Answer 1

The correct option is B

10 degrees

$cos3\theta =\frac{\sqrt{3}}{2}=cos\theta$

$3\theta$ $=$ ${30}^{\circ }$

$\theta$ $=$ ${10}^{\circ }$