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Math Help - Quick logic question

  1. #1
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    Quick logic question

    How can i write A /\ B (A and B) using only the signs for negation and the sign for if then (the right facing arrow)

    I know i am supposed to use the changing laws but i cant figure out how.


    Regards
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  2. #2
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    Quote Originally Posted by Monika1987 View Post
    How can i write A /\ B (A and B) using only the signs for negation and the sign for if then (the right facing arrow)

    I know i am supposed to use the changing laws but i cant figure out how.


    Regards
     \neg( A \Rightarrow B ) \Longleftrightarrow A \wedge \neg B --- you can check this with table of truth ( i think that is the term in english, maybe not ( it is just literal translation from my language ) )

    so

    you need  A \wedge B \Longleftrightarrow A \wedge  \neg(\neg B) \Longleftrightarrow \neg( A \Rightarrow \neg B )

    what a mistake!!!
    Last edited by josipive; March 11th 2010 at 07:29 AM.
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  3. #3
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    Quote Originally Posted by Monika1987 View Post
    How can i write A /\ B (A and B) using only the signs for negation and the sign for if then (the right facing arrow)
    Actually it is A \wedge B \equiv \neg \left( {A \to \neg B} \right).
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