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Please help:logic question

  1. Sep 24, 2008 #1
    ok guys this is from my logics course!!!!

    this question may be very simple but i am just gettin stuck

    give a recursive definition of the length of a well formed formula that is of the number of the symbols occuring in it. For example length of (p^(~q)) is 8.
     
  2. jcsd
  3. Sep 24, 2008 #2

    CompuChip

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    OK, so if p is an atomic formula, the length is 1.
    What possibilities do you have to make a new wff out of two wffs p and q?
    For example, if p is a wff of length n, then (~p) is one of length n + 3.
    If p and q are wff's of length n and m, respectively, then (p^q) is of length m+n+3.
     
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