CPM Homework Help : PCT Problem 11-76

Multiply $\cos(\frac { \pi } { 5 }) + i \sin(\frac { \pi } { 5 })$ by its conjugate and simplify.

Step:

$\left( \cos\left( \frac{\pi}{5} \right) +\textit{i}\sin\left( \frac{\pi}{5} \right) \right)\left( \cos\left( \frac{\pi}{5} \right) -\textit{i}\sin\left( \frac{\pi}{5} \right) \right)$