Textbook Question
Use any method to evaluate the integrals in Exercises 55–66.
∫ (x + 2) / (x³ - 2x² - 3x) dx
Ch. 8 - Techniques of Integration
Hass15th EditionThomas' CalculusISBN: 9780137616077
Not the one you use?Change textbookSelect a different textbook
Table of contents
- Ch. 1 - Functions155
- Ch. 2 - Limits and Continuity240
- Ch. 3 - Derivatives337
- Ch. 4 - Applications of Derivatives293
- Ch. 5 - Integrals41
- Ch. 6 - Applications of Definite Integrals25
- Ch. 7 - Transcendental Functions490
- Ch. 8 - Techniques of Integration399
- Ch. 9 - First-Order Differential Equations66
- Ch. 10 - Infinite Sequences and Series132
- Ch. 11 - Parametric Equations and Polar Coordinates58
Chapter 8, Problem 8.2.68
In Exercises 67–73, use integration by parts to establish the reduction formula.
∫ x^n sin(x) dx = -x^n cos(x) + n ∫ x^(n-1) cos(x) dx
Verified step by step guidance1
Identify the parts for integration by parts: let \(u = x^n\) and \(dv = \sin(x) \, dx\).
Compute the derivatives and integrals needed: \(du = n x^{n-1} \, dx\) and \(v = -\cos(x)\) (since \(\frac{d}{dx}(-\cos(x)) = \sin(x)\)).
Apply the integration by parts formula: \(\int u \, dv = uv - \int v \, du\), which gives \(\int x^n \sin(x) \, dx = -x^n \cos(x) - \int (-\cos(x)) (n x^{n-1}) \, dx\).
Simplify the integral expression: \(-x^n \cos(x) + n \int x^{n-1} \cos(x) \, dx\).
This establishes the reduction formula: \(\int x^n \sin(x) \, dx = -x^n \cos(x) + n \int x^{n-1} \cos(x) \, dx\).
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
4mWas this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
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 appropriately is crucial to simplify the integral effectively.
Recommended video:
06:18
Integration by Parts for Definite Integrals
Reduction Formula
A reduction formula expresses an integral involving a parameter (like n) in terms of a similar integral with a lower parameter value. It helps solve integrals recursively by breaking them down step-by-step, making complex integrals manageable through repeated application.
Recommended video:
Guided course
5:59Recursive Formulas
Handling Powers of x in Integration
When integrating expressions like x^n multiplied by trigonometric functions, powers of x are reduced systematically. Differentiating x^n reduces the power by one, which is essential in forming the reduction formula and simplifying the integral through repeated integration by parts.
Recommended video:
05:58Intro to Power Series
Related Practice
Textbook Question
Evaluate the integrals in Exercises 1–22.
∫₀^π 8 sin⁴(y) cos²(y) dy
1
views
Textbook Question
Use the table of integrals at the back of the text to evaluate the integrals in Exercises 1–26.
∫ √(x - x²) / x dx
Textbook Question
Use any method to evaluate the integrals in Exercises 15–38. Most will require trigonometric substitutions, but some can be evaluated by other methods.
∫ (x² dx) / (x² - 1)^(5/2), where x > 1
Textbook Question
Find the average value of f(x) = (√(x + 1)) / √x on the interval [1, 3].
Textbook Question
Use any method to evaluate the integrals in Exercises 55–66.
∫ 2 / (x(ln x - 2)³) dx
1
views