Every sequence of real bounded functions has convergent sub?

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SUMMARY

The discussion centers on the convergence of subsequences of real bounded functions when the input belongs to a finite set of rational numbers, specifically denoted as ##S = \{ x_1,...,x_p\} \subset \mathbb{Q}##. The user demonstrates that for each element in the set, a converging subsequence can be derived, ultimately leading to the conclusion that ##\{ f_{(\sigma_p\circ ... \circ \sigma_1)(n)}(x_i)\}## converges to ##f(x_i)## for all ##i = 1... p##. This iterative process confirms the existence of convergent subsequences for each rational input.

PREREQUISITES
  • Understanding of real analysis concepts, particularly bounded sequences.
  • Familiarity with subsequences and their convergence properties.
  • Knowledge of rational numbers and their properties in mathematical analysis.
  • Basic grasp of function notation and limits in calculus.
NEXT STEPS
  • Study the properties of bounded sequences in real analysis.
  • Learn about the Bolzano-Weierstrass theorem and its implications for convergence.
  • Explore the concept of subsequences and their role in analysis.
  • Investigate the behavior of sequences of functions and uniform convergence.
USEFUL FOR

Mathematicians, students of real analysis, and anyone interested in the convergence properties of sequences and functions, particularly in the context of rational numbers.

RBG
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I figured it out... how do I remove this question?
 
Last edited:
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I don't know the answer, but I have an answer in the case ##x## belongs to finite set of rationals ##S = \{ x_1,...,x_p\} \subset \mathbb{Q}##. It may or may not be useful for what you want to prove.

  1. ## \{f_n(x_1) \}## is a real bounded sequence so there is a converging subsequence ## \{f_{\sigma_1(n)}(x_1) \}## that converges to ##f(x_1)##
  2. ## \{f_{\sigma_1(n)}(x_2) \}## is a real bounded sequence so there is a converging subsequence ## \{f_{(\sigma_2 \circ \sigma_1)(n)}(x_2) \}## that converges to ##f(x_2)##. Furthermore ## \{f_{(\sigma_2 \circ \sigma_1)(n)}(x_1) \}## converges to ##f(x_1)## as a subsequence of ## \{f_{\sigma_1(n)}(x_1) \}##.
  3. Repeating this process, you have ##\{ f_{(\sigma_p\circ ... \circ \sigma_1)(n)}(x_i)\} ## convergerges to ##f(x_i)## for all ##i = 1... p##.
 
RBG said:
I figured it out... how do I remove this question?
Why remove the question?

Wouldn't it be more helpful to other members of the forum to leave the question, and post the answer (or at least an outline of the answer)?
 
Last edited:

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