Trigonometry (10th Edition)

Published by Pearson
ISBN 10: 0321671775
ISBN 13: 978-0-32167-177-6

Chapter 5 - Review Exercises - Page 242: 25

Answer

$$\cos300^\circ=\cos^2150^\circ-\sin^2150^\circ$$ 25 is matched with F.

Work Step by Step

$$\cos300^\circ$$ We rewrite $300^\circ$ as double the angle $150^\circ$. In detail, $$\cos300^\circ=\cos(2\times150^\circ)$$ This fact points to the use of the double identity for cosine, which states $$\cos(2A)=\cos^2A-\sin^2A$$ Therefore, for $A=150^\circ$: $$\cos300^\circ=\cos^2150^\circ-\sin^2150^\circ$$ The equation indicates that 25 should be matched with F.
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.