# Are Disjoint Set Assertions Commutative?

If I were to say that A intersect B was the empty set, does that imply that B intersect A is also the empty set?

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How could this fail? (It is not a rhetorical question.) –  Andres Caicedo Jan 19 '11 at 23:58

Because $A \cap B = \{ x | x \in A \text{ and } x \in B \}$ and surely "and" is commutative.