Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Published by Pearson
ISBN 10: 0-32193-104-1
ISBN 13: 978-0-32193-104-7

Chapter 5 - Trigonometric Functions - Section 5.3 Properties of the Trigonometric Functions - 5.3 Assess Your Understanding - Page 417: 19



Work Step by Step

$\cos{(\theta+ 2 \pi k}) = \cos{\theta}$ $\therefore \cos{\left(\dfrac{\pi}{4}+ (2 \pi \times 4) \right)} = \cos{\left(\dfrac{\pi}{4} \right)}$ $\cos{\left(\dfrac{\pi}{4} \right) }= \boxed{\dfrac{\sqrt{2}}{2}}$
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