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Apr 4, 2022 at 18:38 vote accept Xeh Deng
Apr 4, 2022 at 18:38 comment added Xeh Deng Oh yes it is just the equivalent definition of the compact set and I did not notice it. Thanks professor!
Apr 4, 2022 at 16:50 comment added Yuval Peres That is the definition of a compact set: Every cover by open sets must have a finite subcover. en.wikipedia.org/wiki/Compact_space#Open_cover_definition
Apr 4, 2022 at 14:52 comment added Xeh Deng Hi, thanks for your comment and I do not quite understand why here "there is a finite subcover S". I mean, why the countable sequence of intervals is not possible here? I do not quite understand this point here... Thx~
Mar 31, 2022 at 20:35 history answered Yuval Peres CC BY-SA 4.0