Sum and Difference Identities

6. Trigonometric Identities and More Equations / Sum and Difference Identities / Problem 5

Problem 5

Determine the exact value of the following trigonometric function without using a calculator.
$\cos\left(\frac{7\pi}{12}\right)$

$\frac{\sqrt6-\sqrt2}{4}$

$\frac{\sqrt6+\sqrt2}{4}$

$\frac{\sqrt2-\sqrt6}{4}$

$\frac{-\sqrt2-\sqrt6}{4}$

Determine the exact value of the following trigonometric function without using a calculator.cos(7π12)\cos\left(\frac{7\pi}{12}\right)cos(127π)