Theorem com12b ≪ | index | src | ≫

theorem com12b (a b c: wff): $ a -> b -> c <-> b -> a -> c $;

Step	Hyp	Ref	Expression
1		id	(a -> b -> c) -> a -> b -> c
2	1	com23	(a -> b -> c) -> b -> a -> c
3		id	(b -> a -> c) -> b -> a -> c
4	3	com23	(b -> a -> c) -> a -> b -> c
5	2, 4	ibii	a -> b -> c <-> b -> a -> c

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)