Understanding uniform continuity....

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Discussion Overview

The discussion revolves around the concept of uniform continuity of a function on the interval [a,c], given that it is uniformly continuous on the subintervals [a,b] and [b,c]. Participants explore the necessity of continuity at the point b and the implications for the epsilon-delta proof of uniform continuity.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants question why continuity at the point b is necessary when δ can be taken as the minimum of δ1 and δ2 for the intervals [a,b] and [b,c].
  • Others argue that continuity must be verified at the joining point b to ensure the overall continuity of the function across [a,c].
  • One participant suggests that a small δ could work for the entire interval [a,c], but others challenge this assumption.
  • There is a discussion about the definition of uniform continuity and its application to open and closed intervals, with some participants attempting to clarify their understanding of the proof structure.
  • Participants express confusion regarding the necessity of considering points x and y in the neighborhood of b and how this relates to the continuity of the function at that point.
  • Some propose that the proof should demonstrate that for every ε, there exists a δ that works for all points, including b, to establish uniform continuity.
  • There is a mention of a lemma regarding continuity on compact sets and its relation to uniform continuity, though not all participants are familiar with the concept of compactness.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the necessity of continuity at point b for proving uniform continuity on [a,c]. There are multiple competing views regarding the application of the epsilon-delta definition and the role of continuity at the joining point.

Contextual Notes

Some participants express uncertainty about the definitions and implications of continuity and uniform continuity, particularly in relation to the epsilon-delta proofs. There are unresolved questions about the assumptions made in the proofs and the necessity of continuity at the point b.

Who May Find This Useful

This discussion may be useful for students and individuals studying real analysis, particularly those interested in the concepts of continuity and uniform continuity, as well as the epsilon-delta definitions and proofs related to these topics.

  • #31
Alpharup said:
Am fully convinced now. Thanks Stephen and Lavinia. g on [a, b] is continuous, so there is left hand continuity at b. Similarly h has Right hand continuity at b. We exploit this property. Once again, am I on right track?

I think you are on the right track, but things would be clearer if you present a self-contained statement of what is to be proven as well as the proof. The text you quote from Spivak refers to "statements (i) and (ii)" without showing what they are.
 
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  • #32
You are right. I should have posted it.
Here is definition of uniform continuity.
Capture1.PNG
 
  • #33
Also about (i) and (ii)
)
Capture2.PNG
 
  • #34
Capture3.PNG
 

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