How to verify if a mapping is quotient.

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To verify if the mapping f: R^3\{(x1,x2,x3):x1=0} → R^2 defined by (x1,x2,x3) |→ (x2/x1, x3/x1) is a quotient map, one must understand the definition of a quotient mapping and its required properties, including continuity and local injectivity. The discussion highlights the importance of specific topologies in both the domain and codomain for testing quotient maps. It suggests that demonstrating at least one nonzero partial derivative can establish local injectivity, which is a step toward proving the mapping is open and thus a quotient. Additionally, there is a query about the existence of continuous maps that are surjective but not open, indicating a need for further exploration of related theorems. The conversation also touches on whether a continuous map being open on any open subspace implies it is open everywhere, emphasizing the need for careful examination of subspaces.
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Prove or disprove that f is a quotient mapping.
f:R^3\{(x1,x2,x3):x1=0}--->R^2 defined by

(x1,x2,x3)|->(x2/x1,x3/x1)
 
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Do you know what the definition of a quotient mapping is?
What properties should it have?
 
You usually need to have specific topologies defined in your domain and codomain, to test whether a map is a quotient map.
 
I would try using directly the definition.

One direction is definition of continuity, what about the other direction?

I'm honestly not sure myself, but I would try to show that: at least one partial derivative in at least one coordinate is nonzero → it is localy injective → it is open → it is quotient.OT: I'm having trouble coming up with surjective continuous map between euclidean spaces that is not open. Is there some theorem about it? It would mean that every such map is quotient, it seems. If the map was not subjective, it would be easy.

Another OT, but vaguely related: If a countinuous map between euclidean spaces was open on any open subspace of domain, would it imply all that map would be open? There doesn't seem to be any way of continuously passing from open map on a subspace to a place where it takes open subset to non-open subset. So the OP would need to just check if some nice subspace is open.
 
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