Theorem syl5bb ≪ | index | src | ≫

theorem syl5bb (a b c d: wff):
  $ b <-> c $ >
  $ a -> (c <-> d) $ >
  $ a -> (b <-> d) $;

Step	Hyp	Ref	Expression
1		hyp h1	b <-> c
2	1	a1i	a -> (b <-> c)
3		hyp h2	a -> (c <-> d)
4	2, 3	bitrd	a -> (b <-> d)

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)