Question

Find the exact value by using a half-angle identity.

cosine of five pi divided by twelve.

Answer 1

\(\bf cos\left(\frac{5\pi}{12}\right)\\
\textit{keep in mind that } \frac{1}{12}\times 2 = \frac{1}{6}\\
cos\left(\frac{5\pi}{12}\right)\implies
cos\left(\cfrac{
\frac{5\pi}{6}
}{
2
}\right)\)

so use the half-angle identity for the cosine then