Theorem bithd ≪ | index | src | ≫

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

Step	Hyp	Ref	Expression
1		hyp h2	a -> c
2	1	a1d	a -> b -> c
3		hyp h1	a -> b
4	3	a1d	a -> c -> b
5	2, 4	ibid	a -> (b <-> c)

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)