Finding a limit of a sequence or proving it diverges

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Homework Help Overview

The discussion revolves around a sequence defined by iterative applications of sine and cosine functions, specifically: sin(1), cos(sin(1)), sin(cos(sin(1))), and so on. Participants are tasked with finding the limit of this sequence or proving that it diverges.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants explore the possibility of proving divergence by identifying subsequences that converge to different limits. Questions arise about the conditions a limit must satisfy, specifically regarding the equations sin(L) = L and cos(L) = L.

Discussion Status

The discussion is active, with participants sharing thoughts on the implications of the limit conditions. Some guidance has been offered regarding the equations that must hold if the sequence converges, although there is no explicit consensus on the outcome of the sequence.

Contextual Notes

Participants note the challenge of finding subsequences that demonstrate divergence, as well as the implications of the limit conditions on the nature of the sequence.

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Homework Statement



Given is a sequence: sin(1), cos(sin(1)), sin(cos(sin(1))) etc. Find the limit of the sequence or prove it diverges.

Homework Equations



?

The Attempt at a Solution



One way to prove a sequence diverges is to find two subsequences which converge to different limits, but I could not find such. I would be thankful for any idea :)
 
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nikolafmf said:

Homework Statement



Given is a sequence: sin(1), cos(sin(1)), sin(cos(sin(1))) etc. Find the limit of the sequence or prove it diverges.


Homework Equations



?

The Attempt at a Solution



One way to prove a sequence diverges is to find two subsequences which converge to different limits, but I could not find such.


I would be thankful for any idea :)

If there is a limit L, then it must satisfy both sin(L)=L and cos(L)=L, mustn't it?
 
Suppose it does converge to some value. What equations could you deduce regarding that value?
[Dick beat me to the Submit, and was a little more generous with the hint.]
 
haruspex said:
Suppose it does converge to some value. What equations could you deduce regarding that value?
[Dick beat me to the Submit, and was a little more generous with the hint.]

Yeah, probably too generous in retrospect. I like yours better as a starter hint.
 
Last edited:
Yes, it is true, it must satisfy both sin(L)=L and cos(L)=L, from which follows that the sequence diverges :)

Thank you very much to both for the help :)
 

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