Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 6 - Section 6.3 - Trigonometric Functions of Angles - 6.3 Exercises - Page 499: 52

Answer

$\sin\theta$ = $- \frac{4}{\sqrt {17}}$ $\cos\theta$ =$ -\frac{1}{\sqrt {17}}$ $\tan\theta$ = 4 $\cot\theta$ =$ \frac{1}{4}$ (given) $\sec\theta$ = $-\sqrt {17}$ $\csc\theta$ =$- \frac{\sqrt {17}}{4}$

Work Step by Step

Considering $\theta$ as reference angle, we may draw a right triangle ABC to calculate other trigonometric functions- In right triangle ABC- Given $\cot\theta$ =$ \frac{x}{y}$ = $ \frac{1}{4}$ (Ignoring sign) Using Pythagorous theorem- $r =\sqrt {x^{2}+y^{2}}$ =$ \sqrt {1^{2}+4^{2}}$ = $\sqrt {17}$ i.e. x= 1, y= 4 and r=$\sqrt {17}$ Given cot is positive and sin is negative, therefore $\theta$ lies in quadrant III, hence- $\sin\theta$ =$ -\frac{y}{r}$ = $- \frac{4}{\sqrt {17}}$ $\cos\theta$ =$ -\frac{x}{r}$ =$ -\frac{1}{\sqrt {17}}$ $\tan\theta$ =$ \frac{y}{x}$ =$\frac{4}{1}$ = 4 $\cot\theta$ =$ \frac{x}{y}$ =$ \frac{1}{4}$ (given) $\sec\theta$ =$ -\frac{r}{x}$ =$ -\frac{\sqrt {17}}{1}$ = $-\sqrt {17}$ $\csc\theta$ =$ -\frac{r}{y}$ =$- \frac{\sqrt {17}}{4}$
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