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: 17

Answer

1. $sin\theta =-\frac{12}{13}$, 2. $cos\theta =-\frac{5}{13}$, 3. $cot\theta =\frac{5}{12}$, 4. $sec\theta =-\frac{13}{5}$, 5. $csc\theta= -\frac{13}{12}$.

Work Step by Step

Given $tan\theta=\frac{12}{5}\gt0$ and $sin\theta\lt0$, we know $\theta$ is in quadrant III, let $y=-12, x=-5$, we have $r=\sqrt {(-12)^2+(-5)^2}=13$, thus: 1. $sin\theta=\frac{y}{r}=-\frac{12}{13}$, 2. $cos\theta=\frac{x}{r}=-\frac{5}{13}$, 3. $cot\theta=\frac{1}{tan\theta}=\frac{5}{12}$, 4. $sec\theta=\frac{1}{cos\theta}=-\frac{13}{5}$, 5. $csc\theta=\frac{1}{sin\theta}=-\frac{13}{12}$.
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