Theorem orrd ≪ | index | src | ≫ 

theorem orrd (a b c: wff): $ a -> c $ > $ a -> b \/ c $;
StepHypRefExpression
1 orr 
c -> b \/ c
2 hyp h 
a -> c
3 1, 2 syl 
a -> b \/ c

Axiom use

axs_prop_calc (ax_1, ax_2, ax_mp)