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# Help with Logic Proof

Wed 7 Dec, 2016 10:28 am
I'm trying to do some proofs for my logic class and a few of them completely stumped, this one in particular

A ⊃ ( Β ⊃ C ) / ( ~C • D ) ⊃ ( B ⊃ ~A )

The only hint my professor gave me was that I need to add either D or ~D to the premises but I just can't get it to work out... can anyone help?
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Ding an Sich

1
Wed 7 Dec, 2016 09:38 pm
@agarry13,
agarry13 wrote:

I'm trying to do some proofs for my logic class and a few of them completely stumped, this one in particular

A ⊃ ( Β ⊃ C ) / ( ~C • D ) ⊃ ( B ⊃ ~A )

The only hint my professor gave me was that I need to add either D or ~D to the premises but I just can't get it to work out... can anyone help?

Two hints: disjunction introduction for either D or ~D, then a lot of assocation to get the result. It's a little tricky.
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Kolyo

1
Thu 8 Dec, 2016 09:21 pm
Here's a more general hint on how to do these:

Before using any of the formal rules, try to explain in English why the argument is valid. Write down your explanation. Then try to see how your reasoning translates into the formal rules. That's how I do it.
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