Metamath Proof Explorer
Description: Lemma for kur14 . Complementation is an involution on the set of
subsets of a topology. (Contributed by Mario Carneiro, 11-Feb-2015)
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Ref |
Expression |
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Hypotheses |
kur14lem.j |
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kur14lem.x |
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kur14lem.k |
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kur14lem.i |
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kur14lem.a |
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Assertion |
kur14lem4 |
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Proof
Step |
Hyp |
Ref |
Expression |
1 |
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kur14lem.j |
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2 |
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kur14lem.x |
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3 |
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kur14lem.k |
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4 |
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kur14lem.i |
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5 |
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kur14lem.a |
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6 |
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dfss4 |
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7 |
5 6
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mpbi |
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