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Topic: Tautology Proof Question
Replies: 1   Last Post: Mar 19, 2012 5:51 AM

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Ashraf Samhouri

Posts: 1
From: Jordan
Registered: 3/19/12
Tautology Proof Question
Posted: Mar 19, 2012 4:51 AM
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Hello guys,

While studying, I've passed through this proof (in the class notes):

Proof that:
( (p v q) ^ (p -> r) ^ (q -> r) ) -> r
is a tautology?

The solution is:
( (p v q) ^ (¬p v r) ^ (¬q v r) ) -> r
( (p ^ ¬p) v (r ^ q) ^ (¬q v r) ) -> r
(F v (q ^ ¬q) v r) -> r
r -> r
¬r v r
.: T

Actually I can't understand the steps, am not sure if the notes are
well-written here, but I'll appreciate any help in explaining the


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