## Trigonometry 7th Edition

$\displaystyle \frac{1}{2}$
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.