### Home > PC > Chapter 11 > Lesson 11.1.4 > Problem11-59

11-59.

Show that $4 \cos (x + \frac { \pi } { 3 }) = 2 \cos x − 2 \sqrt 3 \sin x$

Use the Angle Sum Identity.

$4\left( \cos(\textit{x})\cos\left( \frac{\pi}{3} \right) - \sin(\textit{x})\sin\left( \frac{\pi}{3} \right)\right) =$

Substitute the exact values for sine and cosine of $\frac{π}{3}$. Then simplify.