Are Continuous Functions with Zero Integral a Subspace of C[a,b]?

  • Context: Graduate 
  • Thread starter Thread starter gaborfk
  • Start date Start date
  • Tags Tags
    Functions Subspaces
Click For Summary

Discussion Overview

The discussion revolves around whether the set of continuous functions on the interval [a,b] that have a zero integral is a subspace of the space of continuous functions, C[a,b]. The focus is on the definitions and properties of subspaces in the context of functional analysis.

Discussion Character

  • Homework-related
  • Technical explanation

Main Points Raised

  • One participant seeks help in proving that the set of continuous functions with a zero integral forms a subspace of C[a,b].
  • Another participant suggests starting by checking the definition of a subspace, which involves closure under addition and scalar multiplication.
  • It is noted that to show closure under addition, one must demonstrate that if \(\int_a^b f(x) dx = 0\) and \(\int_a^b g(x) dx = 0\), then \(\int_a^b (f(x) + g(x)) dx = 0\) holds true.
  • Additionally, it is proposed that if \(\int_a^b f(x) dx = 0\), then for any scalar \(k\), \(k \int_a^b f(x) dx = 0\) should also be verified.
  • There is a mention that showing the set is a subset is trivial in this case.

Areas of Agreement / Disagreement

Participants generally agree on the steps needed to verify the properties of a subspace, but the discussion remains focused on the exploration of these properties without reaching a definitive conclusion.

Contextual Notes

Participants have not yet fully explored the implications of the definitions or provided detailed proofs for the claims regarding closure under addition and scalar multiplication.

gaborfk
Messages
53
Reaction score
0
Yet another problem I need to get some starting help on:

Show that the set of continuous functions f=f(x) on [a,b] such that [tex]\int \limits_a^b f(x) dx=0[/tex] is a subspace of C[a,b]
Thank you
 
Physics news on Phys.org
I would start by checking the definition of subspace.
 
Definition of subspace means that the functions are closed under addition and scalar multiplication
 
gaborfk said:
Definition of subspace means that the functions are closed under addition and scalar multiplication

So can you show that that's true for the potential subspace in your example?
 
You mean that if [tex]\int \limits_a^b f(x) dx=0[/tex] and [tex]\int \limits_a^b g(x) dx=0[/tex], can I prove that [tex]\int \limits_a^b f(x)+g(x) dx=0[/tex]? Also, if [tex]\int \limits_a^b f(x) dx=0[/tex] then [tex]k\int \limits_a^b f(x) dx=0[/tex]?
 
Yeah, that's pretty much it. (Technically you also have to show that it's a subset, but in this case that's trivial.)
 
Thank you!

The "hard ones" are so easy sometimes...
 

Similar threads

  • · Replies 19 ·
Replies
19
Views
6K
  • · Replies 6 ·
Replies
6
Views
4K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 7 ·
Replies
7
Views
3K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 27 ·
Replies
27
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K