Theorem imim2d ≪ | index | src | ≫ 

theorem imim2d (a b c d: wff): $ a -> c -> d $ > $ a -> (b -> c) -> b -> d $;
StepHypRefExpression
1 imim2 
(c -> d) -> (b -> c) -> b -> d
2 hyp h 
a -> c -> d
3 1, 2 syl 
a -> (b -> c) -> b -> d

Axiom use

axs_prop_calc (ax_1, ax_2, ax_mp)