Using the Deduction Theorem and the principles of Ex Falso, Reductio ad Absurdum, and Indirect Proof, I am to show that:
(a) $$((A→B)→A)→A$$
and
(b) $$A,B ⊢ ¬(A→¬B)$$
I know how to forumlate the principles mentioned and I also intuitively see that (a) and (b) are valid. My problem, however, is that I actually can't figure out how to use the principle mention to show this ...
I would love it if someone could offers some assistance in showing how we apply the principle in order to show (a) and (b).