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Homework Help: Interesting logic question

  1. Nov 6, 2007 #1
    1. How do you prove, using SD, that ((A>B)>A)>A?

    3. I tried to first assume (A>B)>A. Then I made a sub-derivation, assuming ~A. In this sub-derivation, I need to derive a contradiction. How?
  2. jcsd
  3. Nov 7, 2007 #2


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    Staff Emeritus
    Science Advisor

    What does your symbol ">" mean?
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