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Functional analysis

  1. Jan 27, 2008 #1

    I need help with an analysis proof and I was hoping someone might help me with it. The question is:

    Let (X,d) be a metric space and say A is a subset of X. If x is an accumulation point of A, prove that every r-neighbourhood of x actually contains an infinite number of distinct points of A (where r>0). Using this, prove that any finite subset of X is closed.

    Any help or suggestions would really be appreciated.
  2. jcsd
  3. Jan 27, 2008 #2


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    To get started you'll need to carefully parse the definitions. Closure means all Cauchy sequences converge within the set. How will this apply to a finite set? Can't you show that there is a minimum distance among the points? How will that relate to the definition of a Cauchy sequence?

    I think you're missing an assumption in the first part. Let A be a set of only one point and x be that point. Was A supposed to be a non-empty open subset?
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