Unformatted text preview: ∅ ∈ A × A . Note that by deﬁnition A × A consists of all the ordered pairs ( a, b ) where a, b ∈ A . Thus ( ∅ , ∅ ) ∈ A × A but ∅ 6∈ A × A . (5) Yes, it is true that ( A ∩ Z ) × ( A ∩ Z ) ⊆ B × B . Note that ( A ∩ Z ) = { 1 , 2 } ⊆ B . 1...
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 Spring '08
 JACK
 Math, Sets, Ordered pair, Section B1

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