Theorem sylbir ≪ | index | src | ≫

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

Step	Hyp	Ref	Expression
1		hyp h2	b -> c
2		hyp h1	b <-> a
3	2	bi2i	a -> b
4	1, 3	syl	a -> c

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)