Precalculus: Mathematics for Calculus, 7th Edition

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

Chapter 5 - Section 5.2 - Trigonometric Functions of Real Numbers - 5.2 Exercises - Page 418: 64

Answer

$\displaystyle \sin t=-\frac{24}{25}\quad \tan t=\frac{24}{7}$ $\displaystyle \sec t=-\frac{25}{7}\quad\csc t=-\frac{25}{24}\quad\cot t=\frac{7}{24}$

Work Step by Step

$\sin^{2}t+\cos^{2}t=1\qquad\Rightarrow\sin t=\pm\sqrt{1-\cos^{2}t}$ In quadrant $III$, tan and cot are positive, all the other functions are negative (see table of signs, p.410) So $\sin t=-\sqrt{1-(-\frac{7}{25})^{2}}=-\sqrt{\dfrac{625-49}{625}}$ $=-\displaystyle \sqrt{\frac{576}{625}}=-\frac{24}{25}$ $\displaystyle \tan t=\frac{\sin t}{\cos t}=\frac{-\frac{24}{25}}{-\frac{7}{25}}=\frac{24}{7}$ $\displaystyle \sec t=\frac{1}{\cos t}=-\frac{25}{7}$ $\\$ $\displaystyle \csc t=\frac{1}{\sin t}=-\frac{25}{24}$ $\\$ $\displaystyle \cot t=\frac{1}{\tan t}=\frac{7}{24}$
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