Theorem bibi2 ≪ | index | src | ≫ 

theorem bibi2 (a b: wff): $ b -> (a <-> b <-> a) $;
StepHypRefExpression
1 bicomb 
a <-> b <-> (b <-> a)
2 bibi1 
b -> (b <-> a <-> a)
3 1, 2 syl5bb 
b -> (a <-> b <-> a)

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)