Skip to main content
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 8.2.36

Evaluate the integrals in Exercises 31–56. Some integrals do not require integration by parts.
∫ (ln x)³/x dx

Guida verificata passo dopo passo
1
Recognize that the integral is \( \int \frac{(\ln x)^3}{x} \, dx \). Notice that the integrand involves \( (\ln x)^3 \) divided by \( x \), which suggests a substitution related to \( \ln x \).
Use the substitution \( u = \ln x \). Then, the differential \( du = \frac{1}{x} dx \), which means \( dx = x \, du \). Since \( \frac{1}{x} dx = du \), the integral can be rewritten in terms of \( u \).
Rewrite the integral using the substitution: \( \int (\ln x)^3 \cdot \frac{1}{x} dx = \int u^3 \, du \). This simplifies the integral to a basic power function of \( u \).
Integrate \( u^3 \) with respect to \( u \) using the power rule for integration: \( \int u^n \, du = \frac{u^{n+1}}{n+1} + C \), where here \( n = 3 \).
After integrating, substitute back \( u = \ln x \) to express the answer in terms of \( x \). This completes the evaluation of the integral.

Risposta video verificata per un problema simile:

Questa soluzione video è stata consigliata dai nostri tutor come utile per risolvere questo problema.
Durata del video:
1m

Concetti chiave

Ecco i concetti essenziali che devi comprendere per rispondere correttamente alla domanda.

Integration by Substitution

Integration by substitution simplifies integrals by changing variables to make the integral easier to solve. For example, setting u = ln(x) transforms the integral into a polynomial form in terms of u, which is easier to integrate.
Video consigliato:
04:27
Substitution With an Extra Variable

Properties of Logarithmic Functions

Understanding the natural logarithm function ln(x) and its derivative is crucial. Since d/dx [ln(x)] = 1/x, this relationship helps identify substitution candidates and simplifies integrals involving ln(x).
Video consigliato:
Percorso guidato
06:21
Properties of Functions

Integration of Polynomial Functions

Once substitution reduces the integral to a polynomial form, integrating powers of a variable (like u³) involves applying the power rule for integration: ∫u^n du = u^(n+1)/(n+1) + C, which is straightforward and essential for solving the problem.
Video consigliato:
07:00
Taylor Polynomials