Trigonometry 7th Edition

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

Chapter 6 - Section 6.1 - Solving Trigonometric Equations - 6.1 Problem Set - Page 327: 77

Answer

$$\cos 2A =1-2\sin^2A$$

Work Step by Step

Since \begin{align*} \cos 2A&=\cos^2A-\sin^2A,\ \ \ \ \ \ \ \ \ \text{Use }\cos^2x+\sin^2x=1 \\ &=(1-\sin^2A)-\sin^2A\\ &=1-2\sin^2A \end{align*}
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.