Homework Help: Interesting logic question

1. Nov 6, 2007

Cornelius

1. How do you prove, using SD, that ((A>B)>A)>A?

3. I tried to first assume (A>B)>A. Then I made a sub-derivation, assuming ~A. In this sub-derivation, I need to derive a contradiction. How?

2. Nov 7, 2007

cristo

Staff Emeritus
What does your symbol ">" mean?