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Homework Help: Propositional Logic Question

  1. Jan 14, 2007 #1
    1. The problem statement, all variables and given/known data

    I don't have symbols for negations, so i'll just use the word NOT..

    Prove the validity of the sequents below:

    NOT ( P -> Q) YIELDS Q-> P

    2. Relevant equations

    Relavent deductions as listed here.. http://en.wikipedia.org/wiki/Propositional_logic" [Broken]

    Using things such as ^ elimination/introduction, Modens Ponens,.. etc

    3. The attempt at a solution

    1. NOT ( P -> Q) Premise
    2. NOT Q Assumption
    3. NOT NOT P MT 1,2 (added in extra negation from line 1)
    4. P NOT NOT Elimination
    5. NOT Q -> P

    I"m looking for Q -> P.. which the opposite answer.. i think its something to do with the negations being all wrong.. any help??
    Last edited by a moderator: May 2, 2017
  2. jcsd
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