Calculus with Applications (10th Edition)

Published by Pearson
ISBN 10: 0321749006
ISBN 13: 978-0-32174-900-0

Chapter 13 - The Trigonometric Functions - 13.1 Definitions of the Trigonometric Functions - 13.1 Exercises - Page 678: 20

Answer

$\sin \theta=\frac{3}{5}$ $\cos \theta=\frac{4}{5}$ $\tan \theta=\frac{3}{4}$ $\csc \theta=\frac{5}{3}$ $\sec \theta=\frac{5}{4}$ $\cot \theta=\frac{4}{3}$

Work Step by Step

We are given $x=20,y=15$ $x, y, r$ form a right-angled triangle so to find r we can apply the formula: $x^2+y^2=r^2$ $\rightarrow z=\sqrt 20^2+15^2=25$ With $x=20, y=15, z=25$, thetrigonometric functions are $\sin \theta=\frac{y}{r}=\frac{15}{25}=\frac{3}{5}$ $\cos \theta=\frac{x}{r}=\frac{20}{25}=\frac{4}{5}$ $\tan \theta=\frac{y}{x}=\frac{15}{20}=\frac{3}{4}$ $\csc \theta=\frac{1}{\sin \theta}=\frac{5}{3}$ $\sec \theta=\frac{1}{\cos \theta}=\frac{5}{4}$ $\cot \theta=\frac{x}{y}=\frac{4}{3}$
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