Theorem bieq1 | index | src |

theorem bieq1 (a b c: wff): $ (a <-> b) -> (a <-> c <-> (b <-> c)) $;
StepHypRefExpression
1 id
(a <-> b) -> (a <-> b)
2 1 bieq1d
(a <-> b) -> (a <-> c <-> (b <-> c))

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)