Theorem con2bi ≪ | index | src | ≫

theorem con2bi (a b: wff): $ a -> ~b <-> b -> ~a $;

Step	Hyp	Ref	Expression
1		con2	(a -> ~b) -> b -> ~a
2		con2	(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)