Question

Find an exact value.cos 165°

Answer 1

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