Precalculus (10th Edition)

Published by Pearson
ISBN 10: 0-32197-907-9
ISBN 13: 978-0-32197-907-0

Chapter 8 - Applications of Trigonometric Functions - 8.1 Right Triangle Trigonometry; Applications - 8.1 Assess Your Understanding - Page 519: 13

Answer

$\sin\theta=\dfrac{\sqrt{3}}{2}$ $\cos\theta=\dfrac{1}{2}$ $\tan\theta=\sqrt 3$ $\cot\theta=\dfrac{\sqrt 3}{3}$ $\sec\theta=2$ $\csc\theta=\dfrac{2\sqrt 3}{3}$

Work Step by Step

Let's note: $h$=the hypotenuse $o$=the opposite side of angle $\theta$ $a$=the adjacent side of angle $\theta$ We are given: $h=4$ $a=2$ Determine the opposite side, using the Pythagorean Theorem: $h^2=o^2+a^2$ $4^2=o^2+2^2$ $o^2=12$ $o=\pm\sqrt{12}$ $o=\pm2\sqrt{3}$ Since $h$ is never negative, then $h=2\sqrt3$. Determine the 6 trigonometric functions of angle $\theta$: $\sin\theta=\dfrac{o}{h}=\dfrac{2\sqrt 3}{4}=\dfrac{\sqrt{3}}{2}$ $\cos\theta=\dfrac{a}{h}=\dfrac{2}{4}=\dfrac{1}{2}$ $\tan\theta=\dfrac{o}{a}=\dfrac{2\sqrt 3}{2}=\sqrt 3$ $\cot\theta=\dfrac{a}{o}=\dfrac{2}{2\sqrt 3}=\dfrac{1}{\sqrt 3}=\dfrac{\sqrt 3}{3}$ $\sec\theta=\dfrac{h}{a}=\dfrac{4}{2}=2$ $\csc\theta=\dfrac{h}{o}=\dfrac{4}{2\sqrt 3}=\dfrac{2}{\sqrt 3}=\dfrac{2\sqrt 3}{3}$
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