Originally Posted by **kit**

Hi,

I don't know if this the place to post this question, but I guess I can always try.

My questions are regarding Logic.

1) I'm trying to prove 'proof by cases' - X v Y, X -> Z, Y -> Z |- Z

I'm trying to prove it using the natural rules, but am having problems!

2) Using proof by cases, I want to prove the implication rule: A -> B |- ¬A v B

Either that, or by using natural rules.

This is really starting to annoy me - as I have spent a long time working on this!

Any help / advice would be helpful!

Thanks.

Kit