the question is in the attachment and the format of the proof is in the doc. attachment

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- Mar 1st 2009, 09:27 AMsmh745Direct Proof
the question is in the attachment and the format of the proof is in the doc. attachment

- Mar 1st 2009, 09:54 AMPlato
$\displaystyle \begin{array}{lcr}

1 & {a \to b} & {} \\

2 & {\neg c \to d} & {} \\

3 & {\neg b \vee \neg d} & {} \\

4 & {b \to \neg d} & 3 \\

5 & {a \to \neg d} & {1,4} \\

6 & {d \to \neg a} & 5 \\

7 & {\neg c \to \neg a} & {2,6} \\

8 & {c \vee \neg a} & 7 \\

\end{array} $

Now you supply the correct format and reasons. - Mar 1st 2009, 10:04 AMsmh745
thanx alot that is helped

I appreciated