Logic proof: Philosophy Forums

Logic proof

Christim
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Joined: Feb 28, 2009

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Posted 11/07/09 - 03:46 PM: Subject: Logic proof	#1
Prove or disprove that the following rule of inference is sound: Hint: You can use a truth table, but a careful logical argument will also do it. (p \/ q \/ r) (~p \/ s) --------------- (q \/ r \/ s)

frank2010
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Joined: Oct 11, 2009

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Posted 11/08/09 - 01:00 AM:	#2
Hi, here's my proof: 1) p v (q v r) Assumption 2) ~p v s Assumption 3) ~p -> (q v r) 1 Material Implication 4) p -> s 2 Material Implication 5) ~(q v r) -> p 3 Trasp 6) ~(q v r) -> s 4,5 Syll 7) (q v r) v s 6 Material Implication Q.E.D.

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