Precalculus (6th Edition)

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

Chapter 7 - Trigonometric Identities and Equations - Chapter 7 Test Prep - Review Exercises - Page 738: 100


$\dfrac {\sqrt {10}}{10}$

Work Step by Step

$\cos \left( \arctan x\right) =\dfrac {1}{\sqrt {1+x^{2}}}\Rightarrow \cos \left( \arctan 3\right) =\dfrac {1}{\sqrt {1+3^2}}=\dfrac {\sqrt {10}}{10}$
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