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Ch. 8 - Techniques of Integration
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoHass 15th EditionCh. 8 - Techniques of IntegrationProblema 8.4.24
Capitolo 8, Problema 8.4.24

Use any method to evaluate the integrals in Exercises 15–38. Most will require trigonometric substitutions, but some can be evaluated by other methods.
∫ √(9 - w²) dw / w²

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Identify the integral to solve: \(\int \frac{\sqrt{9 - w^{2}}}{w^{2}} \, dw\).
Recognize that the integrand contains a square root of the form \(\sqrt{a^{2} - w^{2}}\), which suggests using a trigonometric substitution: let \(w = 3 \sin(\theta)\), where \(a = 3\).
Compute the differential: \(dw = 3 \cos(\theta) \, d\theta\). Also, rewrite the expressions inside the integral in terms of \(\theta\): \(\sqrt{9 - w^{2}} = \sqrt{9 - 9 \sin^{2}(\theta)} = 3 \cos(\theta)\) and \(w^{2} = 9 \sin^{2}(\theta)\).
Substitute all parts into the integral to express it entirely in terms of \(\theta\): replace \(\sqrt{9 - w^{2}}\) with \(3 \cos(\theta)\), \(w^{2}\) with \(9 \sin^{2}(\theta)\), and \(dw\) with \(3 \cos(\theta) \, d\theta\). This will simplify the integral to a trigonometric integral.
Simplify the resulting integral and use trigonometric identities to integrate with respect to \(\theta\). After integrating, substitute back \(\theta = \arcsin(\frac{w}{3})\) to express the answer in terms of \(w\).

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Trigonometric Substitution

Trigonometric substitution is a technique used to evaluate integrals involving expressions like √(a² - x²), √(a² + x²), or √(x² - a²). By substituting x with a trigonometric function (e.g., x = a sin θ), the integral simplifies using trigonometric identities, making it easier to solve.
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Introduction to Trigonometric Functions

Integration of Rational Functions

Integration of rational functions involves integrating expressions where the integrand is a ratio of polynomials or functions. Recognizing when to simplify or rewrite the integrand, such as separating terms or using substitution, is essential for solving integrals involving algebraic expressions.
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Intro to Rational Functions

Use of Pythagorean Identities

Pythagorean identities like sin²θ + cos²θ = 1 are fundamental in trigonometric substitution. They allow the conversion of square root expressions into simpler trigonometric forms, facilitating the integration process by reducing complex radicals to manageable trigonometric expressions.
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Solve Trig Equations Using Identity Substitutions
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