TheCoconutChef
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 Jun28 revised Is the intersection of every non-empty family of inductive sets equal to the intersection of every inductive set? deleted 1 characters in body Jun27 comment Is the intersection of every non-empty family of inductive sets equal to the intersection of every inductive set? I don't see why this general version was needed, and my question was about finding a reason for its presence. Jun27 awarded Editor Jun27 revised Is the intersection of every non-empty family of inductive sets equal to the intersection of every inductive set? added 10 characters in body Jun27 comment Is the intersection of every non-empty family of inductive sets equal to the intersection of every inductive set? It's me that should have added the sentence preceding these : "We shall say, temporarily, that a set A is a successor set if [...]" Jun27 asked Is the intersection of every non-empty family of inductive sets equal to the intersection of every inductive set? Dec30 comment I shouldn't be able to prove the power-set of union is equal to union of power-sets. Thanks. The absence of quantifier can be explained by the fact that this problem emerged in the context of Hamos' Naive Set Theory, which makes no use of quantifier and very little of first order logic. It was asked to prove that $P(A) \cup P(B) \subset P(A \cup B)$, and I decided to test the converse, which we aren't asked to do. Dec30 awarded Supporter Dec30 accepted I shouldn't be able to prove the power-set of union is equal to union of power-sets. Dec29 asked I shouldn't be able to prove the power-set of union is equal to union of power-sets. Jul7 comment Understanding this summation identity I guess that when manipulating new symbols (the Sigma notation isn't exactly new to me but it had never been center stage) their complete meaning isn't immediately apparent. I didn't see it concretely. Jul7 awarded Scholar Jul7 accepted Understanding this summation identity Jul7 comment Understanding this summation identity Thanks. Quite helpful. Jul7 comment Understanding this summation identity Didn't expect answers which would come as quickly and be as good. Thanks. Jul7 awarded Student Jul7 asked Understanding this summation identity