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Ch. 5 - Trigonometric Identities
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161당신이 사용하는 게 아니라요?교과서 변경
6장, 문제 5.54

Verify that each equation is an identity.
(sin² θ)/cos θ = sec θ - cos θ

검증된 단계별 안내
1
Start by rewriting the right-hand side of the equation using trigonometric identities: \( \sec \theta = \frac{1}{\cos \theta} \). So, the right-hand side becomes \( \frac{1}{\cos \theta} - \cos \theta \).
Combine the terms on the right-hand side over a common denominator: \( \frac{1}{\cos \theta} - \cos \theta = \frac{1 - \cos^2 \theta}{\cos \theta} \).
Recall the Pythagorean identity: \( \sin^2 \theta + \cos^2 \theta = 1 \). Therefore, \( 1 - \cos^2 \theta = \sin^2 \theta \).
Substitute \( \sin^2 \theta \) for \( 1 - \cos^2 \theta \) in the expression: \( \frac{\sin^2 \theta}{\cos \theta} \).
Observe that the left-hand side of the original equation is \( \frac{\sin^2 \theta}{\cos \theta} \), which matches the transformed right-hand side, thus verifying the identity.

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주요 개념

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

Trigonometric Identities

Trigonometric identities are equations that hold true for all values of the variable where both sides of the equation are defined. Common identities include the Pythagorean identities, reciprocal identities, and co-function identities. Understanding these identities is crucial for verifying equations and simplifying trigonometric expressions.
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Fundamental Trigonometric Identities

Reciprocal Functions

Reciprocal functions in trigonometry relate the sine, cosine, and tangent functions to their reciprocals: cosecant (csc), secant (sec), and cotangent (cot). For example, sec θ is defined as 1/cos θ. Recognizing these relationships is essential for manipulating and verifying trigonometric equations.
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Secant, Cosecant, & Cotangent on the Unit Circle

Algebraic Manipulation

Algebraic manipulation involves rearranging and simplifying equations using algebraic rules. This includes factoring, combining like terms, and applying identities to transform one side of an equation to match the other. Mastery of these techniques is necessary for verifying trigonometric identities effectively.
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Algebraic Operations on Vectors