Theorem bitr4g ≪ | index | src | ≫

theorem bitr4g (a b c d e: wff):
  $ d <-> b $ >
  $ e <-> c $ >
  $ a -> (b <-> c) $ >
  $ a -> (d <-> e) $;

Step	Hyp	Ref	Expression
1		hyp h1	d <-> b
2		bicom	(e <-> c) -> (c <-> e)
3		hyp h2	e <-> c
4	2, 3	ax_mp	c <-> e
5		hyp h	a -> (b <-> c)
6	4, 5	syl6bb	a -> (b <-> e)
7	1, 6	syl5bb	a -> (d <-> e)

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)