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Logical Proof

  1. Sep 10, 2007 #1
    Prove x <=> y is logically equivalent to (x-->y) ^ ((~x)-->(~y)).
  2. jcsd
  3. Sep 10, 2007 #2
    Please show some sort of work or at least tell us where you are stuck. We help with your homework, not do your homework.
  4. Sep 10, 2007 #3


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    Actually, [itex]x \Leftrightarrow y[/itex] is shorthand for a longer expression. Which one? Now rewrite one of the subexpressions and you're done.

    If you want more specific help, please refer to l46kok's post.

    Also, how specific do you need the proof to be? Can you use "intuitive" rules or do you really have to produce a proof tree?
    Last edited: Sep 10, 2007
  5. Sep 10, 2007 #4
    I'd just use a truth table.

    If you don't know what that is, then I don't think you belong in math.
  6. Sep 10, 2007 #5

    matt grime

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    Rubbish. If you do know what one is then perhaps you belong in computer science or electrical engineering?
  7. Sep 10, 2007 #6
    Aoik: what is the contrapositive of ~x=>~y

    p.s.: Matt, you crack me up.
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