Theorem mtd ≪ | index | src | ≫

theorem mtd (a b c: wff): $ a -> ~b $ > $ a -> c -> b $ > $ a -> ~c $;

Step	Hyp	Ref	Expression
1		hyp h1	a -> ~b
2		hyp h2	a -> c -> b
3	2	con3d	a -> ~b -> ~c
4	1, 3	mpd	a -> ~c

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)