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What does this mean? Whats the difference between IFF and IF?

  1. Jun 24, 2011 #1
    What does this mean? Whats the difference between IFF and IF?
     
  2. jcsd
  3. Jun 24, 2011 #2

    Borek

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    Staff: Mentor

  4. Jun 25, 2011 #3

    mathman

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    Re: Iff

    Logical implication A -> B can be expressed as if A then B.

    A -> B and B -> A can be expressed as iff A then B.
     
  5. Jun 25, 2011 #4
    Re: Iff

    Oh, I see now.

    A<->B is iff

    and A->B is if
     
  6. Jun 25, 2011 #5
    Re: Iff

    Another way to think about it is that [itex]A \Leftrightarrow B[/itex] means that [itex]A[/itex] and [itex]B[/itex] have the same truth value. Either both are true or both are false.

    If you are asked to do a proof of an IFF statement, you should break it down into two proofs: one of [itex]A \Rightarrow B[/itex] and the other of [itex]B \Rightarrow A[/itex]. Typically one direction will be easier than the other.
     
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