Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Published by Pearson
ISBN 10: 0-32193-104-1
ISBN 13: 978-0-32193-104-7

Chapter 7 - Applications of Trigonometric Functions - Section 7.1 Right Triangle Trigonometry ; Applications - 7.1 Assess Your Understanding - Page 540: 9

Answer

$\sin\theta=\dfrac{5}{13}$ $\cos\theta=\dfrac{12}{13}$ $\tan\theta=\dfrac{5}{12}$ $\csc\theta=\dfrac{13}{5}$ $\sec\theta=\dfrac{13}{12}$ $\cot\theta=\dfrac{12}{5}$

Work Step by Step

First, we have to calculate the third side of the triangle. We can use the Pythagorean Theorem: $$c^2=a^2+b^2 \quad\text{ where $c$ is the hypotenuse}$$. $5^2+12^2=c^2$ $25+144=c^2$ $169=c^2$ $13=c$ Now we can calculate all six trigonometric functions for $\theta$ using their definitions: $\sin\theta=\dfrac{\text{Opposite}}{\text{Hypotenuse}}=\dfrac{5}{13}$ $\cos\theta=\dfrac{\text{Adjacent}}{\text{Hypotenuse}}=\dfrac{12}{13}$ $\tan\theta=\dfrac{\text{Opposite}}{\text{Adjacent}}=\dfrac{5}{12}$ $\csc\theta=\dfrac{\text{Hypotenuse}}{\text{Opposite}}=\dfrac{13}{5}$ $\sec\theta=\dfrac{\text{Hypotenuse}}{\text{Adjacent}}=\dfrac{13}{12}$ $\cot\theta=\dfrac{\text{Adjacent}}{\text{Opposite}}=\dfrac{12}{5}$
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