Trigonometry 7th Edition

Published by Cengage Learning
ISBN 10: 1111826854
ISBN 13: 978-1-11182-685-7

Chapter 1 - Section 1.4 - Introduction to Identities - 1.4 Problem Set - Page 40: 48

Answer

$\sin\theta$ = - $\frac{2\sqrt 2}{3}$ $\tan\theta$ = $2\sqrt 2$ $\csc\theta$ = -$\frac{3}{2\sqrt2}$ $\sec\theta$ = -3 $\cot\theta$ = $\frac{1}{2\sqrt 2}$

Work Step by Step

We know from first Pythagorean identity that- $\sin\theta$ = ± $\sqrt (1-\cos^{2}\theta)$ Given $\cos\theta$ is negative and $\theta$ is not in QII, therefore $\theta$ terminates in Q III. Hence $\sin\theta$ will be negative- OR $\sin\theta$ = - $\sqrt (1-\cos^{2}\theta)$ substitute the given value of $\cos\theta$- $\sin\theta$= - $\sqrt (1-(\frac{-1}{3})^{2})$ $\sin\theta$ = - $\sqrt (1-\frac{1}{9})$ $\sin\theta$ = - $\sqrt (\frac{9-1}{9})$ = - $\sqrt (\frac{8}{9})$ $\sin\theta$ = - $\frac{2\sqrt 2}{3}$ By ratio identity- $\tan\theta$ = $\frac{\sin\theta}{\cos\theta}$ Substituting the values of $\sin\theta$ and $\cos\theta$- $\tan\theta$ = $\frac{-2\sqrt 2/3}{ -1/3}$ = $2\sqrt 2$ From reciprocal identities- $\csc\theta$ = $\frac{1}{\sin\theta}$ = $\frac{1}{-2\sqrt2/3}$ = -$\frac{3}{2\sqrt2}$ $\sec\theta$ = $\frac{1}{\cos\theta}$ = $\frac{1}{-1/3}$ = -3 $\cot\theta$ = $\frac{1}{\tan\theta}$ = $\frac{1}{2\sqrt 2}$
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