Theorem syl6bbr | index | src |

theorem syl6bbr (a b c d: wff):
  $ d <-> c $ >
  $ a -> (b <-> c) $ >
  $ a -> (b <-> d) $;
StepHypRefExpression
1 bicom
(d <-> c) -> (c <-> d)
2 hyp h1
d <-> c
3 1, 2 ax_mp
c <-> d
4 hyp h2
a -> (b <-> c)
5 3, 4 syl6bb
a -> (b <-> d)

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)