Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 5 - Section 5.2 - Trigonometric Functions of Real Numbers - 5.2 Exercises - Page 417: 38

Answer

(a) $\cos{0.8} \approx 0.70$ (b) $\cos{0.8} \approx 0.70$ The values are the same.

Work Step by Step

RECALL: $\sin{t} = y \\\cos{t} =x$ (a) The value of $\color{red}\cos{\color{red}0\color{red}.\color{red}8}$ is equal to the x-coordinate of the red point shown in the attached image below. Thus, using the given figure, $\color{red}\cos{\color{red}0\color{red}.} \color{red}8\color{red}\approx \color{red}0\color{red}.\color{red}7\color{red}0$. (b) Using a calculator in RAD mode gives: $\cos{0.8} \approx 0.70$ The two values are the same.
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