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Homework Help: Logic help

  1. Oct 6, 2004 #1
    need to prove this

    [tex]
    \frac{\urcorner P \equiv false}{P \equiv true}
    [/tex]

    here is what I did
    using Leibniz

    [tex]
    \frac{X \equiv Y}{E[z:=X] \equiv E[z:=Y]}
    [/tex]

    [tex]
    X=\urcorner P
    [/tex]

    [tex]
    Y=false
    [/tex]

    [tex]
    E:\urcorner z
    [/tex]

    [tex]
    z=z
    [/tex]

    [tex]
    \frac{\urcorner P \equiv false}{\urcorner\urcorner P \equiv \urcorner false}
    [/tex]

    since [tex]\urcorner\urcorner P \equiv P[/tex]
    and [tex]\urcorner false \equiv true [/tex]

    [tex]
    \frac{\urcorner P \equiv false}{P \equiv true}
    [/tex]

    is this a proof?
     
  2. jcsd
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