Hello How to prove the min function is continuous?

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Discussion Overview

The discussion revolves around proving the continuity of the minimum function, specifically for two functions \( f_1 \) and \( f_2 \) mapping from a set \( X \) to the real numbers, where \( f_3 = \min\{f_1, f_2\} \). The scope includes theoretical aspects of continuity and mathematical reasoning.

Discussion Character

  • Exploratory, Technical explanation, Homework-related, Mathematical reasoning

Main Points Raised

  • One participant inquires about how to prove the continuity of the function \( f_3 = \min\{f_1, f_2\} \).
  • Another participant presumes that \( f_1 \) and \( f_2 \) are continuous and suggests separating the analysis into cases where \( f_1(x) \neq f_2(x) \) and \( f_1(x) = f_2(x) \).
  • A later reply mentions using the gluing lemma as a convenient approach to construct the proof.
  • Another participant provides a quick solution by expressing the minimum function in terms of \( f \) and \( g \) using the formula \( \min(f, g) = \frac{f+g}{2} - \frac{|f-g|}{2} \).

Areas of Agreement / Disagreement

Participants have not reached a consensus on the proof method, and multiple approaches are presented without resolving which is preferable.

Contextual Notes

Assumptions about the continuity of \( f_1 \) and \( f_2 \) are not explicitly confirmed, and the discussion does not clarify the implications of the cases suggested for the proof.

simpleeyelid
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Hello!

Could anybody give me an idea about this proof?

knowing f_{i}:X\rightarrowR i=1,2

to show whether f_{3}=min{f_{1},f_{2}} is continuous!

Thanks in advance,

Regards
 
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Presumably f1 and f2 are continuous themselves? Is this a homework problem? I'll give you a small hint: work on the points where f1(x)=/=f2(x) and f1(x)=f2(x) separately
 
yeah, thanks, a lot, I finally find that it is convenient to construct it using the gluing lemma.
 
quick solution:

min(f, g) = (f+g)/2 - |f-g|/2
 

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