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Ch. 8 - Techniques of Integration
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Not the one you use?Change textbook
All textbooksHass 15th EditionCh. 8 - Techniques of IntegrationProblem 8.4.52
Chapter 8, Problem 8.4.52

For Exercises 49–52, complete the square before using an appropriate trigonometric substitution.
∫ √(x² + 2x + 2) / (x² + 2x + 1) dx

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Start by completing the square for the expressions inside the integral. For the numerator's radicand \(x^2 + 2x + 2\), rewrite it as \(x^2 + 2x + 1 + 1\), which can be expressed as \((x + 1)^2 + 1\).
Similarly, complete the square for the denominator \(x^2 + 2x + 1\), which is already a perfect square and can be written as \((x + 1)^2\).
Rewrite the integral using these completed squares: \(\int \frac{\sqrt{(x + 1)^2 + 1}}{(x + 1)^2} \, dx\).
Make the substitution \(u = x + 1\), so the integral becomes \(\int \frac{\sqrt{u^2 + 1}}{u^2} \, du\).
Use a trigonometric substitution appropriate for \(\sqrt{u^2 + 1}\), such as \(u = \tan \theta\), which implies \(\sqrt{u^2 + 1} = \sec \theta\). Then express \(du\) in terms of \(d\theta\) and rewrite the integral accordingly.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Completing the Square

Completing the square is a technique used to rewrite quadratic expressions in the form (x + a)² + b. This simplifies the integrand and helps identify suitable substitutions, especially for integrals involving square roots of quadratic expressions.
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Completing the Square to Rewrite the Integrand

Trigonometric Substitution

Trigonometric substitution replaces algebraic expressions with trigonometric functions to simplify integrals involving square roots of quadratic forms. The substitution depends on the form a² ± x² or x² ± a², converting the integral into a trigonometric integral that is easier to evaluate.
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Introduction to Trigonometric Functions

Integration of Rational Functions Involving Quadratics

Integrals with rational functions containing quadratic polynomials often require algebraic manipulation and substitution. Understanding how to simplify the denominator and numerator, especially after completing the square, is essential to apply substitution methods effectively.
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Integrals Involving Natural Logs: Substitution Example 7
Related Practice
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