Theorem mpbird ≪ | index | src | ≫

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

Step	Hyp	Ref	Expression
1		hyp h2	a -> b
2		hyp h1	a -> (c <-> b)
3	2	bi2d	a -> b -> c
4	1, 3	mpd	a -> c

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)