Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 7 - Trigonometric Identities and Equations - 7.1 Fundamental Identities - 7.1 Exercises: 78

Answer

$-\tan ^{2}\theta $

Work Step by Step

$-sec^{2}\left( -\theta \right) +\sin ^{2}\left( -\theta \right) +\cos ^{2}\left( -\theta \right) =-sec^{2}\left( -\theta \right) +1=1-\dfrac {1}{\cos ^{2}\left( -\theta \right) }=1-\dfrac {1}{\cos ^{2}\theta }=\dfrac {\cos ^{2}\theta -1}{\cos ^{2}\theta }=\dfrac {-\sin ^{2}\theta }{\cos ^{2}\theta }=-\tan ^{2}\theta $
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