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[(A -> B)->A]->A

... i started off by assuming [(A -> B)->A] then assume ~A to try to derive A in the end... but now i'm stuck :(

and also:

Suppose we dropped from SD the rule for vE, and adopted in its place the rule of Disjunctive Syllogism (DS), thus giving a modified system SD. Show that

you can derive the SD rule for vE in SD.

I have no idea how to even approach the second question.. any help would be greatly appreciated.. thanks! :D