Show that a mapping is continuous

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Homework Help Overview

The problem involves demonstrating the continuity of a mapping defined from a subset of E^{n+1} to another point in the same space. The mapping takes points (x_{1}, x_{2}, ..., x_{n+1}) and transforms them into a new form involving their magnitudes.

Discussion Character

  • Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss various definitions of continuity and explore how to apply them to the given mapping. There is an attempt to find an open set in the range of the function to show the inverse image is open in the domain. Questions arise regarding the nature of limit points and how to prove the convergence of sequences under the mapping.

Discussion Status

The discussion is ongoing, with participants sharing definitions of continuity and suggesting approaches to the proof. Some participants express uncertainty about specific steps, such as identifying limit points and the implications of given assumptions.

Contextual Notes

There is a focus on the definitions of continuity provided, and participants are navigating how these definitions apply to the specific mapping in question. The original poster is seeking assistance in understanding how to proceed with the proof.

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Homework Statement


Show that the mapping f carrying each point [itex](x_{1},x_{2},...,x_{n+1})[/itex] of [itex]E^{n+1}-0[/itex] onto the point [itex](\frac{x_{1}}{|x|^{2}},...,\frac{x_{n+1}}{|x|^{2}})[/itex] is continuous.

2. Continuity theorems I am given.
A transformation f:S->T is continuous provided that if p is a limit point of a subset X of S then f(p) is a limit point or a point of f(X).

Let f:S->T be a transformation of space S into space T. A necessary and sufficient condition that f be continuous is that if O is an open subset of T, then its inverse image [itex]f^{-1}(O)[/itex] is open in S.

A necessary an sufficient condition that the transformation f:S->T be continuous is that if x is a point of S, and V is an open subset of T containing f(x) then there is an open set U in S containing x and such that f(U) lies in V.

The Attempt at a Solution


I was thinking to prove this I would have to find an open set in the range of this function and show that its inverse image is also open in the domain but I am not sure how I would go about doing that.

Any help would be appreciated.
 
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What is the definition of continuity you work with?
 
I have three. They are

A transformation f:S->T is continuous provided that if p is a limit point of a subset X of S then f(p) is a limit point or a point of f(X).

Let f:S->T be a transformation of space S into space T. A necessary and sufficient condition that f be continuous is that if O is an open subset of T, then its inverse image f^(-1)(O) is open in S.

A necessary an sufficient condition that the transformation f:S->T be continuous is that if x is a point of S, and V is an open subset of T containing f(x) then there is an open set U in S containing x and such that f(U) lies in V.

I updated the original post to reflect this.
 
I would use the first one. Given a sequence ## \mathbf{x}^{(n)} \rightarrow \mathbf{p} ##, prove that ## \frac {\mathbf{x}^{(n)}} {(x^{(n)})^2} \rightarrow \frac {\mathbf{p}} {p^2} ##.
 
voko said:
I would use the first one. Given a sequence ## \mathbf{x}^{(n)} \rightarrow \mathbf{p} ##, prove that ## \frac {\mathbf{x}^{(n)}} {(x^{(n)})^2} \rightarrow \frac {\mathbf{p}} {p^2} ##.

I don't really understand. Can you elaborate a little bit? I don't know how I would show that a point [itex]x=(x_{1},x_{2},...,x_{n+1})[/itex] is a limit point.
 
You don't have to prove ## \mathbf{x}^{(n)} \rightarrow \mathbf{p} ##, this is an assumption. Given that assumption, prove ## \frac {\mathbf{x}^{(n)}} {(x^{(n)})^2} \rightarrow \frac {\mathbf{p}} {p^2} ##.
 

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