Precalculus (10th Edition)

Published by Pearson
ISBN 10: 0-32197-907-9
ISBN 13: 978-0-32197-907-0

Chapter 6 - Trigonometric Functions - 6.3 Properties of the Trigonometric Functions - 6.3 Assess Your Understanding - Page 394: 18



Work Step by Step

$\sec{\alpha} =\sec{\left( \alpha -360^o\right)} \\\Rightarrow \sec{420^o}=\sec{\left( 420^o-360^o\right)} \\=\sec{60^o} \\=\dfrac {1}{\cos 60^o} \\=\dfrac {1}{\cos \dfrac {\pi }{3}} \\=\dfrac {1}{\frac {1}{2}} \\=2$
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