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Interior points proof where one set is a subset of the other

  1. Oct 24, 2013 #1


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    How would I go about proving that if A is a subset of B then the interior points of A are a subset of the interior points of B?
  2. jcsd
  3. Oct 25, 2013 #2
    What did you try?? Where are you stuck? What is your definition of interior point?
  4. Oct 25, 2013 #3


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    If a is an interior point of A, the there is an open set Q in A containing a. Since A is a subset of B, a and Q are in B. Therefore a is an interior point of B.
  5. Oct 25, 2013 #4
    It would have been so much better if you let the OP find this himself.
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