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 5.70

Capitolo 6, Problema 5.70

Verify that each equation is an identity.
(cot² t - 1)/(1 + cot² t) = 1 - 2 sin² t

Guida verificata passo dopo passo

Step 1: Recall the Pythagorean identity: \(1 + \cot^2 t = \csc^2 t\).

Step 2: Substitute \(\csc^2 t\) for \(1 + \cot^2 t\) in the left-hand side of the equation: \((\cot^2 t - 1)/\csc^2 t\).

Step 3: Use the identity \(\csc^2 t = 1/\sin^2 t\) to rewrite the expression: \((\cot^2 t - 1) \cdot \sin^2 t\).

Step 4: Recall that \(\cot^2 t = \cos^2 t/\sin^2 t\), and substitute it into the expression: \((\cos^2 t/\sin^2 t - 1) \cdot \sin^2 t\).

Step 5: Simplify the expression to show that it equals \(1 - 2\sin^2 t\), verifying the 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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Percorso guidato

5:32

Fundamental Trigonometric Identities

Cotangent Function

The cotangent function, denoted as cot(t), is the reciprocal of the tangent function, defined as cot(t) = cos(t)/sin(t). It can also be expressed in terms of sine and cosine, which is essential for manipulating and simplifying trigonometric expressions. Recognizing how cotangent relates to other trigonometric functions is key to solving the given equation.

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Percorso guidato

5:37

Introduction to Cotangent Graph

Sine Function and Its Relationship to Cotangent

The sine function, sin(t), is a fundamental trigonometric function that relates to the cotangent function through the identity cot(t) = cos(t)/sin(t). The expression 1 - 2sin²(t) can be derived from the double angle formulas and is often used in conjunction with cotangent to verify identities. Understanding this relationship helps in transforming and equating both sides of the given equation.

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Percorso guidato

5:53

Graph of Sine and Cosine Function

Pratica correlata

Domanda del libro di testo

Find sinθ.

csc θ = -8/5

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Domanda del libro di testo

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.

1 + cot(-θ)/cot(-θ)

786

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Domanda del libro di testo

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 - sin θ

825

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Domanda del libro di testo

Find the remaining five trigonometric functions of θ.

csc θ = -5/2, θ in quadrant III

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Domanda del libro di testo

Verify that each equation is an identity.

tan α/sec α = sin α

877

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