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How to prove Distractive dilemma ?

  1. Aug 7, 2013 #1
    [ [(p-->q) and (r-->s)] and (~q or ~s) ] --> (~p or ~r)

    I know all basic theories in Logic and I want to know the correct way/correct steps of proving this kind of things? I'm a beginner.. please help

    I can explain above dilemma in words, but I have no idea how to write down the proof correctly.
  2. jcsd
  3. Aug 8, 2013 #2

    Stephen Tashi

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    Science Advisor

    There isn't a single standard for doing proofs that is correct. In a logic course, you would be given certain permissible patterns to use in a proof and you would naturally be expected to use them. (It's also taught in logic courses that proofs can be done by using truth tables.) If this problem arose in a discussion in a calculus course, it would probably be acceptable to offer a proof in words. You have to explain in what context you wish to give a proof.

    Also, I don't think the names of proof techniques used in logic books are completely standardized, so a person might have to be familiar with the book or materials you are using in order to advise you.
  4. Aug 8, 2013 #3


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    Homework Helper

    Proving it by contradiction may be the easiest way. See if you can do that.
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