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Unformatted text preview: a i in turn and deciding whether or not to include it in X . This gives us n independent choices between two possibilities: in X or out. The number of different subsets we can form is therefore 2 n . An alternative way of explaining this is to assign a or 1 to all the elements a i . Each subset corresponds to a unique binary number with n digits. There are 2 n such posibilities. Another proof will be given in the reasoning course next term, using the socalled induction principle. 2.2.5 Introducing Products The last set construct we consider is the product of two (or arbitrary n ) sets. This constructor forms an essential part of the deFnition of relation discussed in the next section. If we want to describe the relationship John loves Mary, then we require a way of talking about John and Mary at the 11...
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This note was uploaded on 01/02/2010 for the course MATH Math2009 taught by Professor Koskesh during the Spring '09 term at SUNY Empire State.
 Spring '09
 Koskesh
 Math

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