Help with showing infinite series converges/diverges

In summary, an infinite series is a sum of an infinite number of terms and its value depends on the individual values of each term and the pattern in which they are added together. To determine if an infinite series converges or diverges, various tests such as the ratio test, comparison test, or integral test can be used. A convergent series approaches a finite value while a divergent series approaches infinity. An infinite series can converge to a negative value, and the limit comparison test can be used to determine the convergence of a series by comparing it to a known series.
  • #1
coreluccio
35
2

Homework Statement



Determine whether the series converges or diverges

1/2(ln(n+1))^2 from n = 1 to infinity

The Attempt at a Solution



Cannot find anything to compare this series to that will show it diverges. Ratio and root test both fail. Integral test requires integrating to a non-elementary anti derivative. I have no clue how to find a solution to this.
 
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  • #2
You probably mean [itex]\frac{1}{2 \ln(n+1)^2}[/itex], think about comparing it with [itex]\frac{1}{n}[/itex]. Which do you think is larger for large values of n? Now can you prove it?
 

Related to Help with showing infinite series converges/diverges

1. What is an infinite series?

An infinite series is a sum of an infinite number of terms. It can be written in the form of a1 + a2 + a3 + ... + an, where a1, a2, a3, etc. are the terms of the series. The value of an infinite series depends on the individual values of each term and the pattern in which they are added together.

2. How do you determine if an infinite series converges or diverges?

To determine if an infinite series converges or diverges, you can use various tests such as the ratio test, the comparison test, or the integral test. These tests evaluate the behavior of the terms in the series and determine if the series approaches a finite value (converges) or approaches infinity (diverges).

3. What is the difference between a convergent and a divergent series?

A convergent series is one that approaches a finite value as more terms are added, while a divergent series is one that approaches infinity (or negative infinity) as more terms are added. In other words, a convergent series has a finite sum, while a divergent series does not.

4. Can an infinite series converge to a negative value?

Yes, an infinite series can converge to a negative value. This means that the sum of the series will be a negative number. For example, the infinite series 1 - 1 + 1 - 1 + ... converges to the value of 1/2, which is a negative number.

5. How do you use the limit comparison test to determine the convergence of an infinite series?

The limit comparison test compares the behavior of the terms in the given series to those in a known series whose convergence or divergence is already known. To use this test, you take the limit of the ratio of the terms in the given series and the known series. If the limit is a positive finite value, then the two series have the same behavior and will either both converge or both diverge. If the limit is zero or infinity, then the two series have different behavior and the convergence of the given series cannot be determined using this test.

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