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Ch. 5 - Trigonometric Identities
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161당신이 사용하는 게 아니라요?교과서 변경
6장, 문제 5.1.56

Write each expression in terms of sine and cosine, and then simplify the expression so that no quotients appear and all functions are of θ only. See Example 3.
csc θ cos θ tan θ

검증된 단계별 안내
1
Recall the definitions of the trigonometric functions in terms of sine and cosine: \( \csc \theta = \frac{1}{\sin \theta} \), \( \cos \theta = \cos \theta \), and \( \tan \theta = \frac{\sin \theta}{\cos \theta} \).
Rewrite the expression \( \csc \theta \cos \theta \tan \theta \) by substituting these definitions: \( \left( \frac{1}{\sin \theta} \right) \cdot \cos \theta \cdot \left( \frac{\sin \theta}{\cos \theta} \right) \).
Combine the terms by multiplying the fractions and functions: \( \frac{1}{\sin \theta} \times \cos \theta \times \frac{\sin \theta}{\cos \theta} = \frac{1}{\sin \theta} \times \frac{\cos \theta \sin \theta}{\cos \theta} \).
Simplify the expression by canceling common factors in numerator and denominator: \( \frac{1}{\sin \theta} \times \frac{\cos \theta \sin \theta}{\cos \theta} = \frac{1}{\sin \theta} \times \sin \theta = 1 \).
Confirm that the simplified expression contains no quotients and only functions of \( \theta \), completing the simplification.

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주요 개념

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

Reciprocal and Quotient Identities

Trigonometric functions like cosecant (csc) and tangent (tan) can be expressed in terms of sine and cosine using reciprocal and quotient identities. Specifically, csc θ = 1/sin θ and tan θ = sin θ/cos θ. These identities allow rewriting expressions to involve only sine and cosine.
추천 영상:
03:40
Quotients of Complex Numbers in Polar Form

Simplification of Trigonometric Expressions

Simplifying trigonometric expressions involves combining terms, canceling common factors, and eliminating quotients to write the expression in a more compact form. This process often requires substituting identities and carefully manipulating fractions to achieve a form with only sine and cosine functions and no division.
추천 영상:
6:36
Simplifying Trig Expressions

Function Domain and Variable Consistency

When rewriting expressions, it is important to ensure all functions depend on the same variable (θ in this case) and that the domain restrictions are considered. This consistency avoids confusion and ensures the simplified expression accurately represents the original function for all valid θ values.
추천 영상:
3:43
Finding the Domain of an Equation