theorem bitr4d (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 |
bicomd |
a -> (c <-> d) |
| 4 |
1, 3 |
bitrd |
a -> (b <-> d) |
Axiom use
axs_prop_calc
(ax_1,
ax_2,
ax_3,
ax_mp)