Theorem imeq2d ≪ | index | src | ≫

theorem imeq2d (a b c d: wff):
  $ a -> (c <-> d) $ >
  $ a -> (b -> c <-> b -> d) $;

Step	Hyp	Ref	Expression
1		biidd	a -> (b <-> b)
2		hyp h	a -> (c <-> d)
3	1, 2	imeqd	a -> (b -> c <-> b -> d)

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)