Trigonometry (10th Edition)

Published by Pearson
ISBN 10: 0321671775
ISBN 13: 978-0-32167-177-6

Chapter 3 - Radian Measure and the Unit Circle - Section 3.3 The Unit Circle and Circular Functions - 3.3 Exercises - Page 118: 54

Answer

$\displaystyle \sin\theta=-\frac{1}{2}$ $\displaystyle \cos\theta=-\frac{\sqrt{3}}{2}$ $\displaystyle \tan\theta=\frac{\sqrt{3}}{3}$ $\cot\theta=\sqrt{3}$ $\displaystyle \sec\theta=-\frac{2\sqrt{3}}{3}$ $\csc\theta=-2$

Work Step by Step

For any real number $s$ represented by a directed arc on the unit circle, $\sin s=y\quad \cos s=x \quad \displaystyle \tan s=\frac{y}{x} (x\neq 0)$ $\displaystyle \csc s=\frac{1}{y} (y\neq 0)\quad \displaystyle \sec s=\frac{1}{x} (x\neq 0) \displaystyle \quad\cot s=\frac{x}{y} (y\neq 0)$. ------------------- $\displaystyle \sin\theta=y=-\frac{1}{2}$ $\displaystyle \cos\theta=x=-\frac{\sqrt{3}}{2}$ $\displaystyle \tan\theta=\frac{y}{x}=\frac{-\frac{1}{2}}{-\frac{\sqrt{3}}{2}}=-\frac{1}{2}(-\frac{2}{\sqrt{3}})=\frac{1}{\sqrt{3}}$ $\displaystyle =\frac{1}{\sqrt{3}}\cdot\frac{\sqrt{3}}{\sqrt{3}}=\frac{\sqrt{3}}{3}$ $\displaystyle \cot\theta=\frac{x}{y}=\frac{-\frac{\sqrt{3}}{2}}{-\frac{1}{2}}=-\frac{\sqrt{3}}{2}(-\frac{2}{1})=\sqrt{3}$ $\displaystyle \sec\theta=\frac{1}{x}=\frac{1}{-\frac{\sqrt{3}}{2}}=-\frac{2}{\sqrt{3}}\cdot\frac{\sqrt{3}}{\sqrt{3}}=-\frac{2\sqrt{3}}{3}$ $\displaystyle \csc\theta=\frac{1}{y}=\frac{1}{-\frac{1}{2}}=-2$
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