Trigonometry 7th Edition

Published by Cengage Learning
ISBN 10: 1111826854
ISBN 13: 978-1-11182-685-7

Chapter 5 - Section 5.1 - Proving Identities - 5.1 Problem Set - Page 280: 88


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

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.
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.