Infinite Series with log natural Question

In summary, the problem involves determining the convergence of the series ∞ Ʃ (-1)^(k+1) / kln(k) where k=2. The methods explored so far include the divergent test, ratio test, root test, and comparison test. However, none of these tests have been successful in determining the convergence of the series. Instead, it may be more helpful to try an integral test instead.
  • #1
Biosaw
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Homework Statement



Ʃ (-1)^(k+1) / kln(k)
k=2

Homework Equations


integral test, p test, comparison test, limit comparison, ratio test, root test.


The Attempt at a Solution


In class so far we have not learned the alternating series test so i can't use that test.
So far I have done the test for divergent which turned up 0, ratio test which turned up 1, root test which didn't work, and its not a geometric or telescoping series.
I think that the only one that will work is the comparison test but I don't know what to use to compare this function.
 
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  • #2
From your question I gather that you only need to say whether the series converges, not what the limit is.

Never mind my old post, it doesn't seem to help.

[old post]
I am not sure how much you have and haven't seen, but one common approach would be looking at the absolute value and using the triangle inequality to write

[tex]\left| \sum_{k = 2}^\infty \frac{(-1)^{k + 1}}{k \ln k} \right| \le \sum_{k = 2}^\infty \left| \frac{(-1)^{k + 1}}{k \ln k} \right|[/tex]

It may also be useful to note that ln k > 1 for k > 2.
[/old post]


[new hint]
Whichever way you try the comparison test, it will always end up "going the wrong way".
Try an integral test instead.
 
Last edited:

1. What is an infinite series with natural logarithm?

An infinite series with natural logarithm is a mathematical series that is defined using the natural logarithm function, ln(x). It is a sum of terms that involves taking the natural logarithm of each term and adding them together. For example, the infinite series ln(1) + ln(2) + ln(3) + ... is an infinite series with natural logarithm.

2. How do you determine the convergence of an infinite series with natural logarithm?

To determine the convergence of an infinite series with natural logarithm, you can use the integral test, comparison test, or limit comparison test. These tests compare the given series to a known convergent or divergent series and determine if the series with natural logarithm behaves in a similar way.

3. What is the difference between an infinite series with natural logarithm and a regular infinite series?

The main difference between an infinite series with natural logarithm and a regular infinite series is that the terms in an infinite series with natural logarithm involve taking the natural logarithm of each term. This can often make the series more complicated and difficult to work with, but it also allows for unique properties and behaviors.

4. Can an infinite series with natural logarithm have a finite sum?

Yes, an infinite series with natural logarithm can have a finite sum. This is known as a convergent series and means that the terms in the series eventually become very small and approach zero. Therefore, the sum of the series is a finite number.

5. How can infinite series with natural logarithm be applied in real life?

Infinite series with natural logarithm have many applications in fields such as physics, engineering, and economics. They can be used to model natural phenomena, calculate probabilities, and solve differential equations. For example, the natural logarithm function is commonly used in population growth models and interest rate calculations.

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