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Ch. 1 - Trigonometric Functions
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161당신이 사용하는 게 아니라요?교과서 변경
2장, 문제 23

Use the appropriate reciprocal identity to find each function value. Rationalize denominators when applicable. See Example 1.
sin θ , given that csc θ = 1.25

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1
Recall the reciprocal identity relating sine and cosecant: \(\csc \theta = \frac{1}{\sin \theta}\).
Given \(\csc \theta = 1.25\), rewrite this as \(1.25 = \frac{1}{\sin \theta}\).
To find \(\sin \theta\), take the reciprocal of both sides: \(\sin \theta = \frac{1}{1.25}\).
Simplify the fraction \(\frac{1}{1.25}\) by expressing 1.25 as a fraction: \(1.25 = \frac{5}{4}\), so \(\sin \theta = \frac{1}{\frac{5}{4}}\).
Use the property of dividing by a fraction: \(\sin \theta = 1 \times \frac{4}{5} = \frac{4}{5}\). This fraction is already rationalized.

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주요 개념

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

Reciprocal Identities

Reciprocal identities relate trigonometric functions to their reciprocals, such as sine and cosecant. Specifically, sin θ = 1 / csc θ. Understanding this allows you to find one function value when given its reciprocal.
추천 영상:
6:25
Pythagorean Identities

Rationalizing Denominators

Rationalizing denominators involves eliminating any irrational numbers from the denominator of a fraction. This is done by multiplying numerator and denominator by a suitable expression, making the expression simpler and more standard.
추천 영상:
2:58
Rationalizing Denominators

Evaluating Trigonometric Functions from Given Values

When given a trigonometric function value, such as csc θ, you can find related functions like sin θ by applying identities and performing algebraic manipulations. This process often requires careful substitution and simplification.
추천 영상:
7:28
Evaluate Composite Functions - Values Not on Unit Circle