theorem unss2 (A B C: set): $ B C_ C -> A u. B C_ A u. C $;
Step | Hyp | Ref | Expression |
1 |
|
unss |
A u. B C_ A u. C <-> A C_ A u. C /\ B C_ A u. C |
2 |
|
ssun1 |
A C_ A u. C |
3 |
2 |
a1i |
B C_ C -> A C_ A u. C |
4 |
|
ssun2 |
C C_ A u. C |
5 |
|
sstr |
B C_ C -> C C_ A u. C -> B C_ A u. C |
6 |
4, 5 |
mpi |
B C_ C -> B C_ A u. C |
7 |
3, 6 |
iand |
B C_ C -> A C_ A u. C /\ B C_ A u. C |
8 |
1, 7 |
sylibr |
B C_ C -> A u. B C_ A u. C |
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)