Precalculus (10th Edition)

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

Chapter 6 - Trigonometric Functions - Chapter Review - Chapter Test - Page 436: 19

Answer

$\cos\theta=-\dfrac{2\sqrt 6}{7}$ $\tan\theta=-\dfrac{5\sqrt 6}{12}$ $\cot\theta=-\dfrac{2\sqrt 6}{5}$ $\sec\theta=-\dfrac{7\sqrt 6}{12}$ $\csc\theta=\dfrac{7}{5}$

Work Step by Step

Determine $\cos\theta$: $\sin^2\theta+\cos^2\theta=1$ $\cos\theta=\pm\sqrt{1-\sin^2\theta}=\pm\sqrt{1-\left(\dfrac{5}{7}\right)^2}$ $=\pm\sqrt{\dfrac{24}{49}}$ $=\pm\dfrac{2\sqrt 6}{7}$ Because the angle $\theta$ is in Quadrant II, we have: $\cos\theta=-\dfrac{2\sqrt 6}{7}$ Determine $\tan\theta,\cot\theta,\sec\theta,\csc\theta$: $\tan\theta=\dfrac{\sin\theta}{\cos\theta}=\dfrac{\frac{5}{7}}{-\frac{2\sqrt 6}{7}}=-\dfrac{5}{2\sqrt 6}=-\dfrac{5\sqrt 6}{12}$ $\cot\theta=\dfrac{1}{\tan\theta}=\dfrac{1}{-\frac{5}{2\sqrt 6}}=-\frac{5}{2\sqrt 6}=-\dfrac{2\sqrt 6}{5}$ $\sec\theta=\dfrac{1}{\cos\theta}=\dfrac{1}{-\frac{2\sqrt 6}{7}}=-\dfrac{7}{2\sqrt 6}=-\dfrac{7\sqrt 6}{12}$ $\csc\theta=\dfrac{1}{\sin\theta}=\dfrac{1}{\frac{5}{7}}=\dfrac{7}{5}$
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