Thread: Propositional Logic Question View Single Post

## Propositional Logic Question

1. The problem statement, all variables and given/known data

I don't have symbols for negations, so i'll just use the word NOT..

Prove the validity of the sequents below:

NOT ( P -> Q) YIELDS Q-> P

2. Relevant equations

Relavent deductions as listed here.. http://en.wikipedia.org/wiki/Propositional_logic

Using things such as ^ elimination/introduction, Modens Ponens,.. etc

3. The attempt at a solution

1. NOT ( P -> Q) Premise
___
2. NOT Q Assumption
3. NOT NOT P MT 1,2 (added in extra negation from line 1)
4. P NOT NOT Elimination
____
5. NOT Q -> P

I"m looking for Q -> P.. which the opposite answer.. i think its something to do with the negations being all wrong.. any help??

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