Theorem mpbi | index | src |

theorem mpbi (a b: wff): $ a <-> b $ > $ a $ > $ b $;
StepHypRefExpression
1 hyp h1
a <-> b
2 1 bi1i
a -> b
3 hyp h2
a
4 2, 3 ax_mp
b

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)