Ch. 5 - Trigonometric Identities

Lial12th EditionTrigonometryISBN: 9780136552161, 9780135440780, 9780136881117, 9780135440827, 9780135924891Non è quello che usi tu?Cambia libro di testo

Lial 12th Edition

Ch. 5 - Trigonometric Identities

Problema 5.48

Capitolo 6, Problema 5.48

Verify that each equation is an identity.
(tan² α + 1)/ sec α = sec α

Guida verificata passo dopo passo

Start by recalling the Pythagorean identity: \( \tan^2 \alpha + 1 = \sec^2 \alpha \).

Substitute \( \sec^2 \alpha \) for \( \tan^2 \alpha + 1 \) in the left-hand side of the equation, giving \( \frac{\sec^2 \alpha}{\sec \alpha} \).

Simplify the expression \( \frac{\sec^2 \alpha}{\sec \alpha} \) by canceling one \( \sec \alpha \) from the numerator and the denominator, resulting in \( \sec \alpha \).

Observe that the simplified left-hand side \( \sec \alpha \) is equal to the right-hand side \( \sec \alpha \).

Conclude that the original equation \( \frac{\tan^2 \alpha + 1}{\sec \alpha} = \sec \alpha \) is indeed an identity.

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Trigonometric Identities

Trigonometric identities are equations that hold true for all values of the variable where both sides are defined. Common identities include the Pythagorean identities, reciprocal identities, and quotient identities. Understanding these identities is crucial for verifying equations and simplifying expressions in trigonometry.

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Fundamental Trigonometric Identities

Tangent and Secant Functions

The tangent function, tan(α), is defined as the ratio of the opposite side to the adjacent side in a right triangle, or as sin(α)/cos(α). The secant function, sec(α), is the reciprocal of the cosine function, defined as 1/cos(α). Recognizing the relationships between these functions is essential for manipulating and verifying trigonometric equations.

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Graphs of Secant and Cosecant Functions

Algebraic Manipulation

Algebraic manipulation involves rearranging and simplifying expressions using algebraic rules. This includes factoring, expanding, and combining like terms. In the context of trigonometric identities, effective algebraic manipulation allows one to transform one side of an equation to match the other, thereby verifying the identity.

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Algebraic Operations on Vectors

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