Piece-wise continuous functions on the close interval

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Discussion Overview

The discussion revolves around the properties of piece-wise continuous functions defined on a closed interval [a,b] and their relationship to the vector space of all functions on that interval. Participants explore how to demonstrate that the set of piece-wise continuous functions forms a subspace of this vector space, focusing on closure under addition and the inclusion of the zero function.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant asks if showing closure under addition and subtraction is sufficient to demonstrate that D[a,b] is a subspace.
  • Another participant emphasizes the need to show that the zero function is piecewise continuous and suggests reviewing definitions related to vector spaces and piecewise continuous functions.
  • A participant inquires about how to create and operate on two piecewise functions.
  • One participant proposes that if f and g are piecewise continuous, then their sum f+g should also satisfy the definition of piecewise continuity, suggesting that careful consideration of subintervals is necessary.
  • A later reply advises participants to learn the definition of piecewise continuity thoroughly, noting the subtleties involved, such as the nature of the smaller intervals.

Areas of Agreement / Disagreement

Participants generally agree on the need to demonstrate closure properties and the inclusion of the zero function, but there is no consensus on the specific methods or definitions to use, indicating multiple competing views and unresolved questions.

Contextual Notes

Participants mention the importance of understanding the definitions of piecewise continuity and vector spaces, highlighting potential ambiguities regarding the nature of intervals (open or closed) and the need for careful subdivision of intervals.

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Let D[a,b] be the set of piece-wise continuous functions on the close interval [a,b]. Show that D[a,b] is a subspace of the vector space P[a,b] of all functions defined on the interval [a,b].

Can someone get me started? Do I just need to show that they are closed under addition and subtraction? If so, how do I show that? Thanks.
 
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Don't forget to show that the zero function is piecewise continuous. Just go over the definitions of a vector space and piecewise continuous function.
 
How do I make up and write out two piecewise functions and do operations on them?
 
Let f and g be piecewise and continuous (write out the definition, soemthing like, for f there is a partition of [a,b] into finitely many subintervals of nonero length such that f is continuous on each, same for g) then check that f+g sastisfies this definition (which may requiire you to think for a second to porduce the subintervals). i assume you're happy that the sum of continuous functions is continuous.
 
learn the definition of piecewise continuous carefully as it is subtle. (are the smaller intervals open or closed or either?) then subdivide.
 

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