Improper integral convergence or divergence.

In summary, the conversation discusses the use of the Comparison Theorem to determine the convergence or divergence of an integral. The given function is compared to the integral of 1/e^x, but the attempt is not successful since the given function is less than 1/e^x. The question of what function to compare it with remains unanswered.
  • #1
crazy_nuttie
12
0

Homework Statement



Use Comparison Theorem to determine whether the integral is convergent or divergent:

integral from 0 to infinity of: arctan(x) / (2 + e^x)

Should look like this: http://bit.ly/cAhytV

Homework Equations



--

The Attempt at a Solution




I tried to compare this with the integral from 0 to infinity of 1/e^x, but that didnt succeed since 1/e^x converges and the given function is less than 1/e^x. I am not sure what to compare this with
 
Last edited by a moderator:
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  • #2
crazy_nuttie said:

Homework Statement



Use Comparison Theorem to determine whether the integral is convergent or divergent:

integral from 0 to infinity of: arctan(x) / (2 + e^x)

Should look like this: http://bit.ly/cAhytV

Homework Equations



--

The Attempt at a Solution




I tried to compare this with the integral from 0 to infinity of 1/e^x, but that didnt succeed since 1/e^x converges and the given function is less than 1/e^x. I am not sure what to compare this with

Not sure why you chose 1/ex since [itex]\arctan x \le \pi/2[/itex] but not bounded by 1.

Anyway, why wouldn't you have succeeded if your integral is less than a known convergent integral? Your problem would be if your unknown integral was greater than a known convergent integral.
 
Last edited by a moderator:

1. What is an improper integral?

An improper integral is an integral where one or both of the limits of integration are infinite or the integrand function is not defined at one or more points within the interval of integration.

2. How do you determine if an improper integral converges or diverges?

To determine convergence or divergence of an improper integral, you must evaluate the integral using appropriate techniques. If the integral evaluates to a finite value, then it converges. If the integral evaluates to infinity or does not converge, then it diverges.

3. What are some common techniques for evaluating improper integrals?

Some common techniques for evaluating improper integrals include using the limit comparison test, comparison test, Cauchy's convergence criterion, or integration by parts.

4. Can an improper integral converge to a non-finite value?

Yes, it is possible for an improper integral to converge to a non-finite value, such as infinity or negative infinity. This can occur when the integrand function has singularities within the interval of integration or when the limits of integration are infinite.

5. How can you use the Integral Test to determine convergence or divergence of an improper integral?

The Integral Test states that if a function f(x) is continuous, positive, and decreasing on the interval [a,∞), then the improper integral ∫a f(x)dx converges if and only if the infinite series ∑a f(n) converges. Therefore, if the series converges, then the integral also converges, and if the series diverges, then the integral also diverges.

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