Given a set with a subset , the complement (denoted or ) of with respect to is defined as
(1)
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Using set difference notation, the complement is defined by
(2)
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If , then
(3)
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where is the empty set. The complement is implemented in the Wolfram Language as Complement[l, l1, ...].
Given a single set, the second probability axiom gives
(4)
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Using the fact that ,
(5)
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(6)
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This demonstrates that
(7)
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Given two sets,
(8)
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(9)
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