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Unformatted text preview: inverse of R , written R1 , is deFned by a R1 b if and only if b R a . Inverse should not be confused with complement: for example, the inverse of is a parent of is is the child of; if z is the cousin of y , then z is in the complement of is a parent of, but not the inverse. Using the R from example 3.5, the inverse R1 = { (2 , 1) , (3 , 2) , (4 , 3) , (1 , 4) } . If we take the inverse of the inverse of a relation, we recover the original relation: ( R1 )1 = R . D EFINITION 3.8 (C OMPOSITION OF R ELATIONS ) Given R A B and S B C , then the composition of R with S , written R S , is deFned by a R S c if and only if b B. ( a R b b S c ) 19...
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 Spring '09
 Koskesh
 Math

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