Thursday, 12 January 2017

real analysis - The complement of Cantor set over closed interval 0 to1. What is its measure and closure??



Is the complement of Cantor set C still measure zero? Meanwhile, I know its accumulation point is C itself (right?). So its closure would be C, correct? Why??? Notice: I am asking for the complement of Cantor set C over closed interval [0,1].


Answer



Let C be the Cantor set and X=[0,1]C its complement in the unit interval. Then m(X)=m([0,1])m(C)=1, so the complement has measure 1. Furthermore the Cantor set is nowhere dense, so its complement must be dense and thus ¯X=[0,1].


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