Theorem mpbiri ≪ | index | src | ≫

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

Step	Hyp	Ref	Expression
1		hyp h2	a -> (c <-> b)
2		hyp h1	b
3	2	a1i	a -> b
4	1, 3	mpbird	a -> c

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)