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Math Help - Need help on mathematical logic

  1. #1
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    Need help on mathematical logic

    Which of the following propositional forms are tautologies.

    (p implies (q implies r)) implies ((p and not q) or r)

    (p and not q) or (q and not r) or (r and not p)

    I need help in both questions, btw, simplify only, no truth table

    Thanks!
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  2. #2
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    Re: Need help on mathematical logic

    Can you determine whether they are tautologies using other means? How do you prove that something is not a tautology using simplifications?
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    Re: Need help on mathematical logic

    Quote Originally Posted by joseph1125 View Post
    Which of the following propositional forms are tautologies.

    (p implies (q implies r)) implies ((p and not q) or r)

    (p and not q) or (q and not r) or (r and not p)

    I need help in both questions, btw, simplify only, no truth table

    Thanks!
    Assume Definition of tautology: Statement that is always true.

    Write first one as A->B and let p=q=r=F
    Then A is F and B is F so A->B is False. Not a tautology.

    Write second one as AorBorC and let p=q=r=F. Then A,B and C are false so AorBorC is false. Not a tautology.
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