How to prove (x,y) | x and y have at some time, lived in the same country) on a set of all people??
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Originally Posted by tinabaker How to prove (x,y) | x and y have at some time, lived in the same country) on a set of all people?? Prove what? Maybe an equivalence relation?
yes
Originally Posted by tinabaker yes Almost anytime a relation contains same it is an equivalence relation. x is same as x: reflexive. If x is same as y then y is the same as x: symmetric. If x is same as y and y is the same as z then x is same as z: transitive.
Originally Posted by Plato Almost anytime a relation contains same it is an equivalence relation. Ha-ha, I agree, but this time it's not because the mapping from people to countries they lived in is not a function.
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