# Help with logic proof (this should be really basic)

1. Nov 4, 2008

### jamo_

help with logic proof (this "should" be really basic)

Hey I am new to logic (I've just started a masters)

I can't for the life of me prove this using only the natural deduction inference rules:

A --> B |- ¬A v B

I can do it easily in the other direction but I cannot do it in the above direction.

It's annoying as I can do it easily using truth tables!

Any help much appreciated.

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

2. Relevant equations

3. The attempt at a solution