Theorem mti ≪ | index | src | ≫

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

Step	Hyp	Ref	Expression
1		hyp h1	~b
2	1	a1i	a -> ~b
3		hyp h2	a -> c -> b
4	2, 3	mtd	a -> ~c

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)