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Thread: open and closed

  1. #1 open and closed 
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    consider (ℝ,τ) , where τ={∅}∪{u⊆ℝ:{-π,π}⊆u}.
    Is [-4.4] open in (ℝ,τ) ? Justify your answer
    Is (-3,3) closed in (ℝ,τ) ? Justify your answer


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  3. #2 Re: open and closed 
    . DrRocket's Avatar
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    Quote Originally Posted by blbl
    consider (ℝ,τ) , where τ={∅}∪{u⊆ℝ:{-π,π}⊆u}.
    Is [-4.4] open in (ℝ,τ) ? Justify your answer
    Is (-3,3) closed in (ℝ,τ) ? Justify your answer
    This is pretty clearly a homework or test problem from an iintroductory class in point-set topology.

    We will not do your schoolwork for you. That would be cheating.


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