Description: Exchange-type theorem. In a Moore system whose closure operator has the exchange property, if F and G are disjoint from H , ( F u. H ) is independent, F is contained in the closure of ( G u. H ) , and either F or G is finite, then there is a subset q of G equinumerous to F such that ( q u. H ) is independent. This implies the case of Proposition 4.2.1 in FaureFrolicher p. 86 where either ( A \ B ) or ( B \ A ) is finite. The theorem is proven by induction using mreexexlem3d for the base case and mreexexlem4d for the induction step. (Contributed by David Moews, 1-May-2017) Remove dependencies on ax-rep and ax-ac2 . (Revised by Brendan Leahy, 2-Jun-2021)
Ref | Expression | ||
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Hypotheses | mreexexlem2d.1 | |
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mreexexlem2d.2 | |
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mreexexlem2d.3 | |
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mreexexlem2d.4 | |
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mreexexlem2d.5 | |
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mreexexlem2d.6 | |
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mreexexlem2d.7 | |
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mreexexlem2d.8 | |
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mreexexd.9 | |
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Assertion | mreexexd | |