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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 8.8.70

In Exercises 69–80, determine whether the improper integral converges or diverges. If it converges, evaluate the integral.
∫₂^∞ (1 / (x√x)) dx

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Rewrite the integral to a simpler form by expressing the integrand with exponents: \(\int_2^{\infty} \frac{1}{x \sqrt{x}} \, dx = \int_2^{\infty} x^{-1} \cdot x^{-\frac{1}{2}} \, dx = \int_2^{\infty} x^{-\frac{3}{2}} \, dx\).
Recognize that this is an improper integral with an infinite upper limit, so express it as a limit: \(\lim_{t \to \infty} \int_2^{t} x^{-\frac{3}{2}} \, dx\).
Find the antiderivative of the integrand \(x^{-\frac{3}{2}}\). Recall the power rule for integration: \(\int x^n \, dx = \frac{x^{n+1}}{n+1} + C\), where \(n \neq -1\). Here, \(n = -\frac{3}{2}\), so the antiderivative is \(\frac{x^{-\frac{1}{2}}}{-\frac{1}{2}} + C = -2 x^{-\frac{1}{2}} + C\).
Evaluate the definite integral from 2 to \(t\) using the antiderivative: \(\left[-2 x^{-\frac{1}{2}} \right]_2^{t} = -2 t^{-\frac{1}{2}} + 2 \cdot 2^{-\frac{1}{2}}\).
Take the limit as \(t\) approaches infinity: \(\lim_{t \to \infty} \left(-2 t^{-\frac{1}{2}} + 2 \cdot 2^{-\frac{1}{2}}\right)\). Determine if this limit exists (finite) to conclude whether the integral converges or diverges.

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주요 개념

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

Improper Integrals

Improper integrals involve integration over an infinite interval or integrands with infinite discontinuities. To evaluate them, we replace the infinite limit with a variable and take the limit as it approaches infinity, determining if the integral converges or diverges.
추천 영상:
11:11
Improper Integrals: Infinite Intervals

Convergence and Divergence of Integrals

An improper integral converges if its limit exists and is finite; otherwise, it diverges. Testing convergence often involves comparing the integral to known convergent or divergent integrals or evaluating the limit of the integral's antiderivative.
추천 영상:
05:44
Divergence Test (nth Term Test)

Integration of Power Functions

Integrating functions of the form x^n involves using the power rule: ∫x^n dx = (x^(n+1))/(n+1) + C, for n ≠ -1. Recognizing and rewriting the integrand as a power function simplifies the integration process, especially for evaluating improper integrals.
추천 영상:
07:32
Representing Functions as Power Series