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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 8.2.40

Evaluate the integrals in Exercises 31–56. Some integrals do not require integration by parts.
∫ x² sin(x³) dx

Guida verificata passo dopo passo
1
Identify the integral to solve: \(\int x^{2} \sin(x^{3}) \, dx\).
Look for a substitution that simplifies the integral. Notice that the argument of the sine function is \(x^{3}\), and the derivative of \(x^{3}\) is \$3x^{2}$, which is similar to the $x^{2}$ term outside the sine.
Set the substitution: let \(u = x^{3}\). Then, compute the differential: \(du = 3x^{2} \, dx\), which implies \(x^{2} \, dx = \frac{du}{3}\).
Rewrite the integral in terms of \(u\): \(\int x^{2} \sin(x^{3}) \, dx = \int \sin(u) \cdot \frac{du}{3} = \frac{1}{3} \int \sin(u) \, du\).
Integrate \(\sin(u)\) with respect to \(u\): \(\int \sin(u) \, du = -\cos(u) + C\). Then substitute back \(u = x^{3}\) to express the answer in terms of \(x\).

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Concetti chiave

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Substitution Method

The substitution method simplifies integrals by changing variables to transform the integral into a more manageable form. For example, setting u = x³ converts the integral into one involving sin(u), making it easier to integrate.
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Euler's Method

Integration by Parts

Integration by parts is a technique based on the product rule for differentiation, used to integrate products of functions. It is applied when substitution is not straightforward, but in this problem, it may not be necessary.
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Integration by Parts for Definite Integrals

Recognizing When to Use Each Technique

Identifying the most efficient integration method is crucial. Here, recognizing that the integral can be solved by substitution rather than integration by parts saves time and simplifies the process.
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Initial Value Problems