Theorem mtbi ≪ | index | src | ≫

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

Step	Hyp	Ref	Expression
1		bi2	(a <-> b) -> b -> a
2		hyp h1	a <-> b
3	1, 2	ax_mp	b -> a
4		hyp h2	~a
5	3, 4	mt	~b

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)