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Ch. 5 - Trigonometric Identities
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161당신이 사용하는 게 아니라요?교과서 변경
6장, 문제 5.1.22

Find sinθ.
csc θ = -8/5

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Recall the definition of cosecant: \(\csc \theta = \frac{1}{\sin \theta}\). This means \(\sin \theta = \frac{1}{\csc \theta}\).
Substitute the given value of \(\csc \theta = -\frac{8}{5}\) into the equation: \(\sin \theta = \frac{1}{-\frac{8}{5}}\).
Simplify the fraction by multiplying numerator and denominator: \(\sin \theta = -\frac{5}{8}\).
Consider the sign of \(\sin \theta\) based on the quadrant where \(\theta\) lies. Since \(\csc \theta\) is negative, \(\sin \theta\) is also negative, which matches the simplified value.
Conclude that \(\sin \theta = -\frac{5}{8}\), consistent with the given \(\csc \theta\).

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주요 개념

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

Reciprocal Trigonometric Functions

The cosecant function (csc θ) is the reciprocal of the sine function (sin θ), meaning csc θ = 1/sin θ. To find sin θ when given csc θ, you take the reciprocal of the given value.
추천 영상:
6:04
Introduction to Trigonometric Functions

Sign of Trigonometric Functions in Quadrants

The sign of sine and cosecant depends on the quadrant where the angle θ lies. Since csc θ = -8/5 is negative, sin θ must also be negative, indicating θ is in either the third or fourth quadrant.
추천 영상:
6:36
Quadratic Formula

Simplifying and Interpreting Fractional Values

Given csc θ = -8/5, sin θ is the reciprocal, so sin θ = -5/8. Understanding how to simplify and interpret these fractional values is essential for accurate calculation and further problem-solving.
추천 영상:
4:02
Solving Linear Equations with Fractions