Theorem bian1a | index | src |

theorem bian1a (a b: wff): $ (b -> a) -> (a /\ b <-> b) $;
StepHypRefExpression
1 ancomb
a /\ b <-> b /\ a
2 bian2a
(b -> a) -> (b /\ a <-> b)
3 1, 2 syl5bb
(b -> a) -> (a /\ b <-> b)

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)