Theorem bian2 ≪ | index | src | ≫ 

theorem bian2 (a b: wff): $ b -> (a /\ b <-> a) $;
StepHypRefExpression
1 bian2a 
(a -> b) -> (a /\ b <-> a)
2 ax_1 
b -> a -> b
3 1, 2 syl 
b -> (a /\ b <-> a)

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)