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 - Review Exercises - Page 434: 19

Answer

$\cos\theta=-\dfrac{5}{13}$ $\tan\theta=-\dfrac{12}{5}$ $\cot\theta=-\dfrac{5}{12}$ $\sec\theta=-\dfrac{13}{5}$ $\csc\theta=\dfrac{13}{12}$

Work Step by Step

$\sin\theta=\dfrac{12}{13}=\dfrac{y}{r}$ Thus, $y=12$ $r=13$ We find $x$ using the formula $r^2=x^2+y^2$: $r^2=x^2+y^2$ $13^2=x^2+12^2$ $169=x^2+144$ $x^2=25$ $x=\pm\sqrt{25}$ $x=\pm5$ Since the angle is in $\text{Quadrant II}$ where $x$ is negative, then $x=-5$. Compute for $\cos\theta, \tan\theta, \cot\theta,\sec\theta, \csc\theta$: $\cos\theta=\dfrac{x}{r}=\dfrac{-5}{13}=-\dfrac{5}{13}$ $\tan\theta=\dfrac{y}{x}=\dfrac{12}{-5}=-\dfrac{12}{5}$ $\cot\theta=\dfrac{x}{y}=\dfrac{-5}{12}=-\dfrac{5}{12}$ $\sec\theta=\dfrac{r}{x}=\dfrac{13}{-5}=-\dfrac{13}{5}$ $\csc\theta=\dfrac{r}{y}=\dfrac{13}{12}$
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