Theorem a1d ≪ | index | src | ≫ 

theorem a1d (a b c: wff): $ a -> b $ > $ a -> c -> b $;
StepHypRefExpression
1 ax_1 
b -> c -> b
2 hyp h 
a -> b
3 1, 2 syl 
a -> c -> b

Axiom use

axs_prop_calc (ax_1, ax_2, ax_mp)