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 6 - Analytic Trigonometry - Section 6.2 The Inverse Trigonometric Functions (Continued) - 6.2 Assess Your Understanding - Page 481: 71

Answer

$\dfrac{-3}{4}$

Work Step by Step

We know that $ f(x)=\sin(x), h(x)=\tan(x)$ Thus we can write: $h(f^{-1} (\dfrac{ -3}{5}))=\tan (\sin^{-1}(\dfrac{ -3}{5})) $ Suppose that $-\theta=\sin^{-1} (\dfrac{-3}{5})$ We know from SOH-CAH-TOA: $\sin{\theta}=\dfrac{opposite}{hypotenuse}=\dfrac{3}{5}$ To find the missing adjacent side, we use the Pythagorean Theorem: $adjacent^2+3^2=5^2$ $adjacent=\sqrt{(5)^2-(3)^2}=\sqrt {16}=4$ Therefore, $\tan (-\theta)=-\dfrac{opposite}{adjacent}=\dfrac{-3}{4}$ Note that we are in quadrant IV because sine is negative, so the tangent of the angle should be negative, as expected.
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