Theorem bi1 ≪ | index | src | ≫

theorem bi1 (a b: wff): $ (a <-> b) -> a -> b $;

Step	Hyp	Ref	Expression
1		anl	(a -> b) /\ (b -> a) -> a -> b
2	1	conv iff	(a <-> b) -> a -> b

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)