theorem sylibrd (a b c d: wff):
$ a -> b -> c $ >
$ a -> (d <-> c) $ >
$ a -> b -> d $;
Step | Hyp | Ref | Expression |
1 |
|
hyp h1 |
a -> b -> c |
2 |
|
hyp h2 |
a -> (d <-> c) |
3 |
2 |
bi2d |
a -> c -> d |
4 |
1, 3 |
syld |
a -> b -> d |
Axiom use
axs_prop_calc
(ax_1,
ax_2,
ax_3,
ax_mp)