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rumjum
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Homework Statement
If X is a metric space such that every infinite subset has a limit point,
then prove that X is compact.
Homework Equations
Hint from Rudin: X is separable and has a countable base. So, it has
countable subcover {Gn} , n=1,2,3... Now, assume that no finite sub
collection of {Gn} covers X and take complement Fn of Union of {Gn}
n=1,2...n. Now, Fn is nonempty as it shall have some element of X not covered
by the finite subcover of {Gn}. Now, if E is a set that contains one
element from each of Fn, then consider a limit point of E & obtain a
contradiction.
The Attempt at a Solution
My attempt:
I can't understand the last part of the hint as how to obtain a contradiction.
Here is my attempt anyways.Please do help.
Given that X has a countable base , say, {Vn} , such that for all x belongs
to an open space G, x belongs to some Vi. In other words,
Gn = Union of {Vn}, say from i = 1,2...n. (finitely many).
Hence, every open cover of X shall have countable subcover
Now,let there be an open cover G1 U G2 ... Gn U..
such that X is a subset of this cover. And
let there be no sub-cover such that X is a subset of {Gi} i=1,2...n.
(finitely many).
Let Fn = complement of (G1 U G2 ...Gn).i.e, complement of any combinations
of Gi's. Now, Fn is non empty as any finite collection of Gi's do not cover
X. Let us chose a point from each Fn, and form a set E.
Now, E shall be an infinite subset of X as otherwise, there shall be finite
number of Fn's. Hence, E should have a limit point. Let the limit point be
"p".
[I am stuck as to what the contradiction should be]. Pls. help!