Divergence/Convergence for Telescoping series

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Discussion Overview

The discussion revolves around the application of the divergence test to telescoping series, specifically whether the limit of the partial sums can indicate divergence or convergence. Participants explore the conditions under which a telescoping series converges or diverges, and seek clarification on the definitions and rules applicable to these series.

Discussion Character

  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions the application of the divergence test to the partial sum of a telescoping series, suggesting confusion over whether the result indicates divergence.
  • Another participant asserts that it is the term ##a_n## that must tend to zero for divergence to be concluded, not the sum itself.
  • There is a request for clarification on what ##a_n## represents, which is identified as a term of the series.
  • A participant expresses a desire for a general rule to determine convergence or divergence for telescoping series, indicating uncertainty about the process.
  • One participant states that the series ##\sum (b_{n+1}-b_n)## is convergent if and only if the sequence ##b_n## is convergent, but questions arise regarding the necessity of finding the convergence of ##b_n## separately in the provided solution.
  • Another participant claims that the proof of a proposition was restored for the specific example discussed.

Areas of Agreement / Disagreement

Participants express differing views on the application of the divergence test and the conditions for convergence in telescoping series. The discussion remains unresolved, with multiple competing perspectives on the topic.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the terms of the series and the definitions of convergence and divergence, which are not fully explored or clarified.

Neon32
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Can I use the divergence test on the partial sum of the telescoping series?
Lim n>infinity an if not equal zero then it diverges

The example below shows a telescoping series then I found the partial sum and took the limit of it. My question is shouldn't the solution be divergent? Since the result -1+cos 1 is not equal to 0? I'm confused.

upload_2017-3-25_11-45-47.png
 
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that is right i guess
 
Neon32 said:
Lim n>infinity an if not equal zero then it diverges
it is ##a_n## must tend to zero, not the sum :)
 
zwierz said:
it is ##a_n## must tend to zero, not the sum :)

what's ##a_n##?
 
a term of the series
 
zwierz said:
a term of the series

How can I determine convergence/divergence for telescopinc series then?
 
you have already done this
 
zwierz said:
you have already done this
I haven't? the solution is above, however I don't quite understand. I want a general rule to detect convergence/divergence fore telescoping series.
 
The series ##\sum (b_{n+1}-b_n)## is convergent iff the sequence ##b_n## is convergent
 
  • #10
zwierz said:
The series ##\sum (b_{n+1}-b_n)## is convergent iff the sequence ##b_n## is convergent
but he didn't find the convergence of bn sepeartly in the solution above?
 
  • #11
He restored the proof of my proposition for this concrete example
 

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