Question

If $2\cos 2A=\sqrt{3}$ and $A$ is acute, find:

$\sin 3A$ is $\frac{1}{\sqrt{m}}$, m is

Answer 1

Given: $2\cos 2A=\sqrt{3}$
$\cos 2A=\frac{\sqrt{3}}{2}$
$\cos 2A=\cos 30$
$2A=30$
$A={15}^{\circ }$
Now, $\sin 3A=\sin 45=\frac{1}{\sqrt{2}}$