# Direct Proof

• March 1st 2009, 09:27 AM
smh745
Direct Proof
the question is in the attachment and the format of the proof is in the doc. attachment
• March 1st 2009, 09:54 AM
Plato
$\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.
• March 1st 2009, 10:04 AM
smh745
thanx alot that is helped

I appreciated