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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
Capitolo 8, Problema 8.PE.8

Evaluate the integrals in Exercises 1–8 using integration by parts.
∫ x sin(x) cos(x) dx

Guida verificata passo dopo passo
1
Recognize that the integral involves the product of functions: \(x\) and \(\sin(x) \cos(x)\). Integration by parts is suitable here, where we let one part be differentiated and the other integrated.
Use the trigonometric identity to simplify the integrand: \(\sin(x) \cos(x) = \frac{1}{2} \sin(2x)\). So the integral becomes \(\int x \cdot \frac{1}{2} \sin(2x) \, dx = \frac{1}{2} \int x \sin(2x) \, dx\).
Set up integration by parts with \(u = x\) (which simplifies upon differentiation) and \(dv = \sin(2x) \, dx\) (which can be integrated easily). Then compute $du = dx$ and find \(v\) by integrating \(dv\).
Apply the integration by parts formula: \(\int u \, dv = uv - \int v \, du\). Substitute the expressions for \(u\), \(v\), \(du\), and \(dv\) into this formula.
Evaluate the resulting integral \(\int v \, du\) and simplify the expression to write the integral in terms of elementary functions plus the constant of integration.

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Integration by Parts

Integration by parts is a technique derived from the product rule of differentiation. It transforms the integral of a product of functions into simpler integrals using the formula ∫u dv = uv - ∫v du. Choosing u and dv wisely simplifies the problem.
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Trigonometric Identities

Trigonometric identities, such as sin(2x) = 2 sin(x) cos(x), help simplify integrals involving products of sine and cosine. Using these identities can reduce complex expressions into more manageable forms for integration.
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Integration of Basic Trigonometric Functions

Knowing how to integrate basic trigonometric functions like sin(x) and cos(x) is essential. These integrals often appear after applying integration by parts or simplifying expressions, enabling the completion of the integration process.
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