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: 49

Answer

$\sin\theta$= $- \frac{\sqrt {95}}{12}$ $\cos\theta$ =$ \frac{7}{12}$ (given) $\tan\theta$ =$- \frac{\sqrt {95}}{7}$ $\cot\theta$ =$- \frac{7}{\sqrt {95}}$ $\sec\theta$ =$ \frac{12}{7}$ $\csc\theta$ =$- \frac{12}{\sqrt {95}}$

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 $\cos\theta$ =$ \frac{x}{r}$ = $ \frac{7}{12}$ (Ignoring sign) Using Pythagorous theorem- $y =\sqrt {r^{2}-x^{2}}$ =$ \sqrt {12^{2}-7^{2}}$ = $\sqrt {95}$ i.e. x=7, y=$\sqrt {95}$ and r=12 Given cos is positive and sin is negative, therefore $\theta$ lies in quadrant IV, hence- $\sin\theta$ =$ -\frac{y}{r}$ = $- \frac{\sqrt {95}}{12}$ $\cos\theta$ =$ \frac{x}{r}$ =$ \frac{7}{12}$ (given) $\tan\theta$ =$ -\frac{y}{x}$ =$- \frac{\sqrt {95}}{7}$ $\cot\theta$ =$ -\frac{x}{y}$ =$- \frac{7}{\sqrt {95}}$ $\sec\theta$ =$ \frac{r}{x}$ =$ \frac{12}{7}$ $\csc\theta$ =$ -\frac{r}{y}$ =$- \frac{12}{\sqrt {95}}$
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