Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Published by Pearson
ISBN 10: 0-32193-104-1
ISBN 13: 978-0-32193-104-7

Chapter 5 - Trigonometric Functions - Chapter Review - Review Exercises - Page 458: 23

Answer

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

Work Step by Step

Given $cot\theta=-2$ and $\theta$ is in quadrant II, let $x=-2, y=1$, we have $r=\sqrt {(-2)^2+(1)^2}=\sqrt {5}$, thus: $sin\theta=\frac{y}{r}=\frac{\sqrt {5}}{5}$, $cos\theta=\frac{x}{r}=-\frac{2\sqrt {5}}{5}$, $tan\theta=\frac{y}{x}=-\frac{1}{2}$, $sec\theta=\frac{1}{cos\theta}=-\frac{\sqrt {5}}{2}$, $csc\theta=\frac{1}{sin\theta}=\sqrt 5$.
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