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: 23

Answer

$\sin\theta=\dfrac{\sqrt 5}{5}$ $\cos\theta=-\dfrac{2\sqrt 5}{5}$ $\tan\theta=-\dfrac{1}{2}$ $\sec\theta=-\dfrac{\sqrt 5}{2}$ $\csc\theta=\sqrt 5$

Work Step by Step

$\cot\theta=-2=\dfrac{x}{y}$ Since $\theta$ is in $\text{Quadrant II}$, we have: $x=-2$ $y=1$ We find $r$ using the formula $r^2=x^2+y^2$, $r^2=x^2+y^2$ $r^2=(-2)^2+1^2$ $r^2=5$ $r=\pm\sqrt5$ $r=\sqrt 5$ (since $r$ is never negative) Compute for $\sin\theta, \cos\theta,\tan\theta, \sec\theta,\csc\theta$: $\sin\theta=\dfrac{y}{r}=\dfrac{1}{\sqrt 5}=\dfrac{\sqrt 5}{5}$ $\cos\theta=\dfrac{x}{r}=\dfrac{-2}{\sqrt 5}=-\dfrac{2\sqrt 5}{5}$ $\tan\theta=\dfrac{y}{x}=\dfrac{1}{2}=-\dfrac{1}{2}$ $\sec\theta=\dfrac{r}{x}=\dfrac{\sqrt{5}}{-2}=-\dfrac{\sqrt 5}{2}$ $\csc\theta=\dfrac{r}{y}=\dfrac{\sqrt{5}}{1}=\sqrt 5$
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