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Ch. 5 - Trigonometric Identities
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161, 9780135440780, 9780136881117, 9780135440827, 9780135924891Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoLial 12th EditionCh. 5 - Trigonometric IdentitiesProblema 5.41
Capitolo 6, Problema 5.41

Simplify each expression.
±√[(1 - cos 8θ)/(1 + cos 8θ)]

Guida verificata passo dopo passo
1
Recognize that the expression involves a square root of a fraction with trigonometric functions: \(\pm \sqrt{\frac{1 - \cos 8\theta}{1 + \cos 8\theta}}\).
Recall the trigonometric identity for tangent in terms of cosine: \(\tan^2 x = \frac{1 - \cos 2x}{1 + \cos 2x}\). Notice the similarity between this identity and the given expression.
Match the given expression to the identity by setting \(2x = 8\theta\), which implies \(x = 4\theta\). This allows rewriting the expression as \(\pm \sqrt{\tan^2 4\theta}\).
Since the square root of \(\tan^2 4\theta\) is the absolute value of \(\tan 4\theta\), and the expression already includes \(\pm\), simplify to \(\pm \tan 4\theta\).
Conclude that the simplified form of the original expression is \(\pm \tan 4\theta\).

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Trigonometric Identities

Trigonometric identities are equations involving trigonometric functions that hold true for all values within their domains. Key identities like the Pythagorean identity and double-angle formulas help simplify complex expressions by rewriting them in more manageable forms.
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Fundamental Trigonometric Identities

Half-Angle Formulas

Half-angle formulas express trigonometric functions of half an angle in terms of the full angle. For example, sin²(θ) = (1 - cos 2θ)/2 and cos²(θ) = (1 + cos 2θ)/2. These formulas are essential for simplifying expressions involving ratios like (1 - cos α)/(1 + cos α).
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Quadratic Formula

Simplification of Radical Expressions

Simplifying radical expressions involves rewriting square roots in simpler or more recognizable trigonometric forms. Recognizing patterns under the root and applying identities can transform complex radicals into basic trigonometric functions, often removing the radical sign.
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Simplifying Trig Expressions
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Factor each trigonometric expression.

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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.

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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 - sin²(-θ)]/[1 + cot²(-θ)]

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Perform each indicated operation and simplify the result so that there are no quotients.

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Verify that each equation is an identity.

tan² α sin² α = tan² α + cos² α - 1

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