## Algebra 2 (1st Edition)

$\frac{1+\sqrt{3}}{2\sqrt2}$
Using the given identities and the known values: $\cos (\pi/12)=\pm\sqrt{\frac{1+\cos(\pi/6)}{2}}=\sqrt{\frac{1+(\frac{\sqrt3}{2})}{2}}=\frac{1+\sqrt{3}}{2\sqrt2}$