## Precalculus (6th Edition)

$\displaystyle \{\frac{\pi}{3}, \ \ \frac{5\pi}{3}\}$
For a point on the unit circle, the coordinates are ($\cos x,\sin x)$, $x\in[0,2\pi)$ The problem is solved when we find the points for which the x-coordinate is $\displaystyle \frac{1}{2}$, ($\cos x$=$\displaystyle \frac{1}{2}$) Using the given unit circle, we find such points in quadrant I, for $x=\displaystyle \frac{\pi}{3}$ in quadrant IV, for $x=\displaystyle \frac{5\pi}{3}$ Solution set: $\displaystyle \{\frac{\pi}{3}, \ \ \frac{5\pi}{3}\}$