Theorem bior1 | index | src |

theorem bior1 (a b: wff): $ ~a -> (a \/ b <-> b) $;
StepHypRefExpression
1 bior1a
(a -> b) -> (a \/ b <-> b)
2 absurd
~a -> a -> b
3 1, 2 syl
~a -> (a \/ b <-> b)

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)