Precalculus (10th Edition)

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

Chapter 6 - Trigonometric Functions - 6.3 Properties of the Trigonometric Functions - 6.3 Assess Your Understanding - Page 394: 51

Answer

$cos\theta= -\frac{\sqrt 5}{3}$, $tan\theta= -\frac{2\sqrt 5}{5}$, $cot\theta= -\frac{\sqrt 5}{2}$, $sec\theta= -\frac{3\sqrt 5}{5}$, $csc\theta= \frac{3}{2}$.

Work Step by Step

Given $sin\theta=\frac{2}{3}$, let $y=2, r=3$, we can get $x=\sqrt {r^2-y^2}=\sqrt 5$. Use the fact that $tan\theta\lt0,sin\theta\gt0$, thus $\theta$ is in quadrant II to determine the sign of each function: $cos\theta=-\frac{x}{r}=-\frac{\sqrt 5}{3}$, $tan\theta=-\frac{y}{x}=-\frac{2\sqrt 5}{5}$, $cot\theta=-\frac{x}{y}=-\frac{\sqrt 5}{2}$, $sec\theta=-\frac{r}{x}=-\frac{3\sqrt 5}{5}$, $csc\theta=\frac{r}{y}=\frac{3}{2}$.
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