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Math Help - set of all people

  1. #1
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    set of all people

    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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  2. #2
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    Re: set of all people

    Quote Originally Posted by tinabaker View Post
    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?
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  3. #3
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    Re: set of all people

    yes
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  4. #4
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    Re: set of all people

    Quote Originally Posted by tinabaker View Post
    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.
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  5. #5
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    Re: set of all people

    Quote Originally Posted by Plato View Post
    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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