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Ch. 6 - Inverse Circular Functions and Trigonometric Equations
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161당신이 사용하는 게 아니라요?교과서 변경
7장, 문제 47

Solve each equation for exact solutions.
cos⁻¹ x + tan⁻¹ x = π/2

검증된 단계별 안내
1
Recognize that the equation is given as \(\cos^{-1} x + \tan^{-1} x = \frac{\pi}{2}\). Our goal is to find all values of \(x\) that satisfy this equation exactly.
Recall the identity involving inverse trigonometric functions: if \(\cos^{-1} x + \sin^{-1} x = \frac{\pi}{2}\), then we can try to relate \(\tan^{-1} x\) to \(\sin^{-1} x\) or \(\cos^{-1} x\) to simplify the expression.
Use the substitution \(\theta = \cos^{-1} x\), which implies \(x = \cos \theta\) and \(\theta \in [0, \pi]\). Then rewrite the equation as \(\theta + \tan^{-1}(\cos \theta) = \frac{\pi}{2}\).
Isolate \(\tan^{-1}(\cos \theta)\) to get \(\tan^{-1}(\cos \theta) = \frac{\pi}{2} - \theta\). Then take the tangent of both sides to obtain \(\cos \theta = \tan\left(\frac{\pi}{2} - \theta\right)\).
Use the co-function identity \(\tan\left(\frac{\pi}{2} - \theta\right) = \cot \theta = \frac{\cos \theta}{\sin \theta}\). Substitute this back to get \(\cos \theta = \frac{\cos \theta}{\sin \theta}\). From here, solve for \(\theta\) and then find \(x = \cos \theta\).

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주요 개념

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Inverse trigonometric functions, such as cos⁻¹(x) and tan⁻¹(x), return the angle whose trigonometric ratio equals x. They are used to find angles from known ratios and have specific ranges to ensure they are functions. Understanding their definitions and ranges is essential for solving equations involving them.
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