Theorem con1bb | index | src |

theorem con1bb (a b: wff): $ ~a <-> b <-> (~b <-> a) $;
StepHypRefExpression
1 con1b
(~a <-> b) -> (~b <-> a)
2 con1b
(~b <-> a) -> (~a <-> b)
3 1, 2 ibii
~a <-> b <-> (~b <-> a)

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)