Answer
$\displaystyle \frac{1}{2}$
Work Step by Step
Using the table on page 128
(Trigonometric functions for special angles)
$\displaystyle \cos\frac{\pi}{3}=\frac{1}{2}$
To memorize this table, this is what I did:
1. Sine is 0 where cosine is $\pm 1$, and cosine is 0 where sine is $\pm 1$.
2. For $45^{o}$ ($\displaystyle \frac{\pi}{4}$) sine and cosine are equal $\displaystyle \frac{\sqrt{2}}{2}$
3. For $30^{o}$and $60^{o}$ ($\displaystyle \frac{\pi}{6}$ and $\displaystyle \frac{\pi}{3}$), the sine and cosine values are $\displaystyle \frac{1}{2}$ and $\displaystyle \frac{\sqrt{3}}{2}.$
Where sine is one cosine is the other, and the other way around.
Remember: sine of the smaller angle is $\displaystyle \frac{1}{2}.$ Reconstruct the rest.