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Math Help - Contrapositive proof

  1. #1
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    Contrapositive proof

    Having a contrapositive proof in which negation was done by DeMorgan's law, .
    Would it be correct to say that in some proofs just one of the cases, ~P or ~Q is true? If so, would it be enough to stop proving when one of the cases was shown to be true?

    Thanking you in anticipation
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  2. #2
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    Re: Contrapositive proof

    Do I understand correctly that you need to prove \neg(P\land Q) and you want to prove \neg P\lor\neg Q instead? Then yes, to prove a disjunction, it is sufficient to prove one of the disjuncts.
    Thanks from jojo7777777
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