theorem xppi21 (A B C: set) (a: nat): $ a e. Xp A (Xp B C) -> pi21 a e. B $;
| Step | Hyp | Ref | Expression |
|---|
| 1 |
|
xpsnd |
a e. Xp A (Xp B C) -> snd a e. Xp B C |
| 2 |
|
xpfst |
snd a e. Xp B C -> fst (snd a) e. B |
| 3 |
2 |
conv pi21 |
snd a e. Xp B C -> pi21 a e. B |
| 4 |
1, 3 |
rsyl |
a e. Xp A (Xp B C) -> pi21 a e. B |
Axiom use
axs_prop_calc
(ax_1,
ax_2,
ax_3,
ax_mp,
itru),
axs_pred_calc
(ax_gen,
ax_4,
ax_5,
ax_6,
ax_7,
ax_10,
ax_11,
ax_12),
axs_set
(elab,
ax_8),
axs_the
(theid,
the0),
axs_peano
(peano1,
peano2,
peano5,
addeq,
muleq,
add0,
addS,
mul0,
mulS)