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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 37

Solve each equation for exact solutions.
2 arccos (x/3 - π/3) = 2π

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Start by isolating the arccosine expression. Given the equation \(2 \arccos\left(\frac{x}{3} - \frac{\pi}{3}\right) = 2\pi\), divide both sides by 2 to get \(\arccos\left(\frac{x}{3} - \frac{\pi}{3}\right) = \pi\).
Recall the definition and range of the arccosine function: \(\arccos(y)\) returns an angle \(\theta\) such that \(\cos(\theta) = y\) and \(\theta \in [0, \pi]\). Here, \(\arccos\left(\frac{x}{3} - \frac{\pi}{3}\right) = \pi\) means the angle whose cosine is \(\frac{x}{3} - \frac{\pi}{3}\) is \(\pi\).
Use the property of cosine: \(\cos(\pi) = -1\). Set the inside of the arccos equal to \(\cos(\pi)\), so \(\frac{x}{3} - \frac{\pi}{3} = -1\).
Solve the resulting linear equation for \(x\): multiply both sides by 3 to clear the denominator, then isolate \(x\).
Check the solution to ensure it lies within the domain of the arccos function, which requires the argument \(\frac{x}{3} - \frac{\pi}{3}\) to be in the interval \([-1, 1]\).

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Inverse Trigonometric Functions (Arccos)

The arccos function is the inverse of the cosine function, returning the angle whose cosine is a given number. Its principal range is from 0 to π radians. Understanding arccos helps in solving equations where the angle is expressed as arccos of an expression.
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Introduction to Inverse Trig Functions

Solving Trigonometric Equations

Solving trigonometric equations involves isolating the trigonometric function and finding all angles that satisfy the equation within the function's domain. This often requires using inverse functions and considering the periodicity of trigonometric functions to find all solutions.
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How to Solve Linear Trigonometric Equations

Domain and Range Restrictions

When dealing with inverse trig functions, it is crucial to consider the domain of the original function and the range of the inverse function. For arccos, the input must be between -1 and 1, and the output angle lies between 0 and π, which restricts possible solutions.
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Domain and Range of Function Transformations