Theorem mt2d ≪ | index | src | ≫ 

theorem mt2d (a b c: wff): $ a -> c $ > $ a -> b -> ~c $ > $ a -> ~b $;
StepHypRefExpression
1 con2 
(b -> ~c) -> c -> ~b
2 hyp h2 
a -> b -> ~c
3 hyp h1 
a -> c
4 1, 2, 3 sylc 
a -> ~b

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)