Direct Proof

**smh745** · March 1st 2009, 09:27 AM

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

**Plato** · March 1st 2009, 09:54 AM

$\begin{array}{lcr} 1 & {a \to b} & {} \\ 2 & {\neg c \to d} & {} \\ 3 & {\neg b \vee \neg d} & {} \\ 4 & {b \to \neg d} & 3 \\ 5 & {a \to \neg d} & {1,4} \\ 6 & {d \to \neg a} & 5 \\ 7 & {\neg c \to \neg a} & {2,6} \\ 8 & {c \vee \neg a} & 7 \\ \end{array}$
Now you supply the correct format and reasons.

**smh745** · March 1st 2009, 10:04 AM

thanx alot that is helped

I appreciated

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