I'm having a really hard time solving the following proofs in Tomassi's Logic book.

1)

P v Q : (P v R) -> (P v(Q & R))

2)

P : Q -> (P <->Q)

3)

P v (Q v R) : Q v (P v R)

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- February 8th 2009, 12:03 PMunprocessed9Help with a few propositional logic proofs
I'm having a really hard time solving the following proofs in Tomassi's Logic book.

1)

P v Q : (P v R) -> (P v(Q & R))

2)

P : Q -> (P <->Q)

3)

P v (Q v R) : Q v (P v R) - February 8th 2009, 12:45 PMPlato
- February 8th 2009, 12:47 PMunprocessed9
I have to prove the proofs using steps and specific notations (used in the Tomassi Book)

- February 8th 2009, 12:58 PMPlato
I for one have never heard of Tomassi much less his textbook (I taught logic many times).

It would be shear accident if anyone here knows the notation used in a particular text.

So if you want help with this, you are going have to type out the list of rules and notations used in that text. - February 8th 2009, 04:11 PMunprocessed9
- February 10th 2009, 06:27 PMarchidi
Assuming that : means equivalent then No 3 can be solved in the following way:

P v (Q v R) = (P v Q)v R =.................................. ( by associativity)

=(Q v P)v R = .................................................. ..(By commutativity)

=Q v (P v R) .................................................. ......(BY associativity again).

Do you want the rest of the problems solved in this way??