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