Epsilon proof and recursive sequences

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Discussion Overview

The discussion revolves around the application of ε, N proofs to recursively defined sequences, particularly in the context of convergence and limits. Participants explore methods for establishing convergence criteria for such sequences, including nested radicals.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant inquires about the approach to ε, N proofs for recursively defined sequences, seeking insights or reading materials.
  • Another participant suggests looking into cobwebbing and related concepts as potential tools for understanding the topic.
  • A different participant proposes that it may be possible to solve for the sequence explicitly and then apply traditional limit techniques, asking for clarification on the specific sequence in question.
  • A participant mentions their experience with proving limits and convergence of recursive sequences, particularly nested radicals, and expresses confusion about applying the ε definition to recursively defined terms.
  • One participant clarifies their understanding that the limit value is suspected to be known and seeks guidance on finding N such that |a_n - L| < ε for n > N, using an example involving a sequence defined recursively.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the best method for applying ε, N proofs to recursively defined sequences, and multiple viewpoints and approaches are presented without resolution.

Contextual Notes

There are limitations regarding the specific sequences being discussed, as well as the assumptions about known limit values and the recursive definitions themselves, which remain unspecified.

dustbin
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Hi,

I am wondering how one would go about an ε, N proof for a recursively defined sequence. Can anyone direct me to some reading or would like to provide insights of their own? This isn't for a homework problem... just general curiosity which I could not satisfy via search!

Thank you.
 
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Depending on the sequence, you may be able to solve for it explicitly and then take the limit as usual. What sequence are you working with, exactly?
 
I'm not working on any sequence in particular, but I started wondering about it while doing something with infinitely nested radicals. I've proven the limit, convergence, etc., of recursive sequences, including nested radicals. I'm wondering if there is a way of doing a traditional epsilon proof using the definition of a convergent sequence. How do you go about finding an n>N such that |a_n - L | < ε? This confuses me because a_n is given recursively...

Thank you for the links on cobwebbing! That looks interesting and I have never heard of it before.
 
To maybe clarify a bit: I am suggesting that the limit value is already known (or at least the suspected value). Given an ε>0, how do I find N such that |a_n - L | < ε whenever n>N.

For instance, if given the sequence x_1 = 1 and x_(n+1)= sqrt(1+x_n)... yielding sqrt(1+sqrt(1+sqrt(1+...))) which has the limit, if I remember correctly, value being the golden ratio.
 

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