Theorem ibid ≪ | index | src | ≫

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

Step	Hyp	Ref	Expression
1		hyp h1	a -> b -> c
2		hyp h2	a -> c -> b
3	1, 2	iand	a -> (b -> c) /\ (c -> b)
4	3	conv iff	a -> (b <-> c)

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)