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Ch. 8 - Techniques of Integration
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077당신이 사용하는 게 아니라요?교과서 변경
8장, 문제 8.4.12

Evaluate the integrals in Exercises 1–14.
∫ √(y² - 25) / y³ dy, where y > 5

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1
Identify the integral to solve: \(\int \frac{\sqrt{y^{2} - 25}}{y^{3}} \, dy\), with the condition \(y > 5\).
Recognize that the integrand contains a square root of the form \(\sqrt{y^{2} - a^{2}}\), which suggests using a trigonometric substitution. Since \(y > 5\), set \(y = 5 \sec(\theta)\), where \(\theta\) is in the appropriate domain to keep \(y > 5\).
Compute the differential \(dy\) in terms of \(d\theta\): \(dy = 5 \sec(\theta) \tan(\theta) \, d\theta\).
Rewrite the integral in terms of \(\theta\) by substituting \(y = 5 \sec(\theta)\) and \(dy\) as above. Simplify the expression inside the square root and the powers of \(y\) accordingly.
Simplify the resulting integral using trigonometric identities, then integrate with respect to \(\theta\). After integration, substitute back \(\theta = \sec^{-1}(\frac{y}{5})\) to express the answer in terms of \(y\).

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Integration of Rational Functions Involving Radicals

This concept involves integrating functions where the integrand contains radicals combined with rational expressions. Techniques often include algebraic manipulation or substitution to simplify the integrand into a more manageable form for integration.
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Integrals Involving Natural Logs: Substitution

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Trigonometric substitution is a method used to evaluate integrals containing expressions like √(y² - a²). By substituting y = a sec(θ), the radical simplifies using trigonometric identities, making the integral easier to solve.
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Introduction to Trigonometric Functions

Definite Domain Considerations and Variable Restrictions

When integrating functions with radicals, the domain restrictions (e.g., y > 5) ensure the expression under the square root is non-negative. Recognizing these constraints is essential to choose the correct substitution and interpret the integral's result properly.
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Definition of the Definite Integral