Question

Find an exact value.cos 165°

Answer 1

$\begin{gathered} \cos 165 \\ \\ \cos 165=\cos (\frac{330}{2}) \\ \\ \pm\sqrt[]{\frac{1+\cos 330}{2}} \\ \\ -\frac{\sqrt[]{1+\cos 330}}{4} \\ \frac{-\sqrt[]{6}-\sqrt[]{2}}{4} \end{gathered}$