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Homework Statement
Let X and Y be ordered sets in the order topology.
I want to show that a function f:X→Y is injective. We are given that f is surjective and preserves order.
Homework Equations
Definition of an order preserving map:
If x≤y implies f(x)≤f(y)
The Attempt at a Solution
So if we assume that it is not injective then we are assuming that f(x)=f(y) and x[itex]\neq[/itex]y.
Then either x>y or y<x. Assuming both, would clearly be a contradiction since it can only be one or the other in an ordered set.
Now I need to show that x>y raises a contradiction and similarly x<y also raises a contradiction.
My main question here is if x<y is it a contradiction if f(x)=f(y)?
It seems like if order is preserved then if x<y then f(x)<f(y)
but by the definition, it appears that if x<y then f(x)<f(y) or f(x)=f(y).
Thank you for your time.
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