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Ch. 3 - Radian Measure and The Unit Circle
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161당신이 사용하는 게 아니라요?교과서 변경
4장, 문제 67

Find the exact value of s in the given interval that has the given circular function value.


[π/2, π] ; sin s = 1/2

검증된 단계별 안내
1
Identify the given interval for the variable \(s\), which is \(\left[\frac{\pi}{2}, \pi\right]\), and the equation \(\sin s = \frac{1}{2}\).
Recall the unit circle values where \(\sin s = \frac{1}{2}\). The sine function equals \(\frac{1}{2}\) at angles \(\frac{\pi}{6}\) and \(\frac{5\pi}{6}\) within one full rotation \([0, 2\pi]\).
Determine which of these angles lie within the given interval \(\left[\frac{\pi}{2}, \pi\right]\). Since \(\frac{\pi}{6}\) is less than \(\frac{\pi}{2}\), it is excluded, but \(\frac{5\pi}{6}\) lies within the interval.
Conclude that the exact value of \(s\) in the interval \(\left[\frac{\pi}{2}, \pi\right]\) satisfying \(\sin s = \frac{1}{2}\) is \(s = \frac{5\pi}{6}\).
Verify the solution by substituting \(s = \frac{5\pi}{6}\) back into the sine function to confirm \(\sin \left(\frac{5\pi}{6}\right) = \frac{1}{2}\).

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주요 개념

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

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The unit circle is a circle with radius 1 centered at the origin, used to define trigonometric functions. Reference angles help find sine values by relating any angle to an acute angle in the first quadrant, simplifying the determination of exact trigonometric values.
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The sine function gives the y-coordinate on the unit circle and is positive in the first and second quadrants. Knowing sine’s symmetry helps identify all angles within a given interval that share the same sine value, such as sin s = 1/2.
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Interval Restriction and Solution Selection

When solving trigonometric equations, restricting the solution to a specific interval ensures the answer fits the problem’s domain. For s in [π/2, π], only angles within this range are considered, which helps select the correct exact value of s.
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