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Thread: Formal proof/truth table

  1. December 7th 2007, 03:25 PM #1
    *skywalker*
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    Formal proof/truth table

    How to use a formal proof in order to show that an argument is valid.

    How to use a truth table to show that an argument is valid.
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  2. December 7th 2007, 03:56 PM #2
    topsquark
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    Quote Originally Posted by *skywalker* View Post
    How to use a formal proof in order to show that an argument is valid.

    How to use a truth table to show that an argument is valid.
    Post a related question and we can help you with it.

    -Dan
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  3. December 7th 2007, 04:15 PM #3
    *skywalker*
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    Quote Originally Posted by topsquark View Post
    Post a related question and we can help you with it.

    -Dan
    the attached document shows the question that this was with!!
    Attached Files Attached Files
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  4. December 7th 2007, 05:43 PM #4
    Plato
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    J-“Juliet takes the drug”; C-“Juliet is caught”; R-“Romeo thinks Juliet is dead”; D(R)-“Romeo is dead”; and D(J)-“Juliet is dead”.

    Argument:
    \begin{array}{l}<br /> \sim J \to C \\ <br /> J \to R \\ <br /> R \to D(R) \\ <br /> \underline {D(R) \to D(J)} \\ <br /> \sim C \to \left( {D(R)D(J)} \right) \\ <br /> \end{array}

    Proof
    \begin{array}{l}<br /> \sim C \to J\quad (1) \\ <br /> \sim C \to R \\ <br /> \sim C \to D(R) \\ <br /> \sim C \to D(J) \\ <br /> C \vee D(R) \\ <br /> C \vee D(J) \\ <br /> \left( {C \vee D(R)} \right) \wedge \left( {C \vee D(J)} \right) \\ <br /> \underline {C \vee \left( {D(R) \wedge D(J)} \right)} \\ <br /> \sim C \to \left( {D(R) \wedge D(J)} \right) \\ <br /> \end{array}

    You fill in the reasons.

    In a truth table we need 2^5 rows. WHY?
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