Trigonometry 7th Edition

Published by Cengage Learning
ISBN 10: 1111826854
ISBN 13: 978-1-11182-685-7

Chapter 1 - Section 1.3 - Definition I: Trigonometric Functions - 1.3 Problem Set - Page 33: 56

Answer

$\sin\theta$ = $ - \frac{7}{25}$ $\tan\theta$ = $ - \frac{7}{24}$ $\cot\theta$ = $ - \frac{24}{7}$ $\sec\theta$ =$ \frac{25}{24}$ $\csc\theta$ = $ - \frac{25}{7}$

Work Step by Step

Given- $\cos\theta$ = $\frac{24}{25}$ and $\theta$ terminates in QIV Therefore $\frac{x}{r}$ = $\frac{24}{25}$ We may consider $x = 24$ and $r = 25$ As $x^{2} + y^{2}$ = $r^{2}$ Therefore $y$ = $\sqrt {r^{2} - x^{2}}$ = $\sqrt {25^{2} - 24^{2}}$ Or $y$ = $\sqrt {625 - 576}$ = $\sqrt {49}$ = $± 7$ As $\theta$ terminates in QIV, y will be negative Therefore, $y$ = $-7$ i.e $x = 24$, $y$ = $-7$ and $r = 25$ Now we can write all T-functions of $\theta$ using Definition-I as following- $\sin\theta$ =$ \frac{y}{r}$ = $ \frac{-7}{25}$ = $ - \frac{7}{25}$ $\tan\theta$ =$ \frac{y}{x}$ =$ \frac{-7}{24}$ = $ - \frac{7}{24}$ $\cot\theta$ =$ \frac{x}{y}$ =$ \frac{24}{-7}$ = $ - \frac{24}{7}$ $\sec\theta$ =$ \frac{r}{x}$ =$ \frac{25}{24}$ $\csc\theta$ =$ \frac{r}{y}$ =$ \frac{25}{-7}$ = $ - \frac{25}{7}$
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