It's just unfortunate terminology -- a closed set is one whose complement is ope... | Hacker News

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		akalin on Jan 31, 2022 \| parent \| context \| favorite \| on: Examples of common false beliefs in mathematics It's just unfortunate terminology -- a closed set is one whose complement is open, not one which is not open.

prof-dr-ir on Jan 31, 2022 [–]

Indeed. Sets are not doors, as the saying goes, because they can be open and closed at the same time.

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