Understanding Improper Integrals with Limits at Infinity

In summary, an improper integral is an integral with infinite limits or an unbounded integrand. It differs from a regular integral which has finite limits and a bounded integrand. The main methods for evaluating an improper integral are the limit comparison test and the comparison test. Possible outcomes of evaluating an improper integral are convergent, divergent, or conditionally convergent. Improper integrals have various real-world applications in fields such as physics, engineering, and economics, including calculating areas, probabilities, and expected values.
  • #1
sinequanon
6
0

Homework Statement



[tex]\int(2dx/(x^2+4)[/tex]
from x= -[tex]\infty[/tex] to x=2

Homework Equations



No specific ones.

The Attempt at a Solution



So, from there I tried to split the integral into two, integrating between 2 and -2, and -2 and -[tex]\infty[/tex], but I got very lost trying to take the limits for these, partly because I don't know what to set as the approaching variables in each case. And integrating the function actually is another issue. Could someone take a look?
 
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  • #2
I think you need to integrate that over.

[tex]\int \frac{1}{x^2+4} \neq lnG(x)[/tex]
 

1. What is an improper integral?

An improper integral is an integral in which one or both of the limits of integration are infinite or the integrand is unbounded at one or more points within the interval of integration.

2. How is an improper integral different from a regular integral?

A regular integral has finite limits of integration and the integrand is bounded within the interval of integration. An improper integral, on the other hand, has infinite limits of integration or an unbounded integrand, which makes it more challenging to evaluate.

3. What are the methods for evaluating an improper integral?

The two main methods for evaluating an improper integral are the limit comparison test and the comparison test. The limit comparison test compares the improper integral to a known convergent or divergent integral, while the comparison test compares the integrand to a simpler function whose convergence is known. Other methods include the integral test, the alternating series test, and the ratio test.

4. What are the possible outcomes of evaluating an improper integral?

An improper integral can have three possible outcomes: it can be convergent, divergent, or conditionally convergent. A convergent improper integral has a finite value, while a divergent improper integral has an infinite value. A conditionally convergent improper integral has a finite value, but the integral of the absolute value of the integrand is infinite.

5. How can improper integrals be applied in real-world situations?

Improper integrals have many applications in physics, engineering, and economics. For example, they can be used to calculate the area under a curve for a function with infinite limits, such as when calculating work or displacement. They can also be used to model real-world situations, such as calculating the probability of an event occurring or determining the expected value of a random variable.

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