Proof of Theorem sbthlem7
| Step | Hyp | Ref
 | Expression | 
| 1 |   | funres 5299 | 
. . 3
⊢ (Fun
𝑓 → Fun (𝑓 ↾ ∪ 𝐷)) | 
| 2 |   | funres 5299 | 
. . 3
⊢ (Fun
◡𝑔 → Fun (◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷))) | 
| 3 |   | dmres 4967 | 
. . . . . . . . 9
⊢ dom
(𝑓 ↾ ∪ 𝐷) =
(∪ 𝐷 ∩ dom 𝑓) | 
| 4 |   | inss1 3383 | 
. . . . . . . . 9
⊢ (∪ 𝐷
∩ dom 𝑓) ⊆ ∪ 𝐷 | 
| 5 | 3, 4 | eqsstri 3215 | 
. . . . . . . 8
⊢ dom
(𝑓 ↾ ∪ 𝐷)
⊆ ∪ 𝐷 | 
| 6 |   | ssrin 3388 | 
. . . . . . . 8
⊢ (dom
(𝑓 ↾ ∪ 𝐷)
⊆ ∪ 𝐷 → (dom (𝑓 ↾ ∪ 𝐷) ∩ dom (◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷))) ⊆ (∪ 𝐷
∩ dom (◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷)))) | 
| 7 | 5, 6 | ax-mp 5 | 
. . . . . . 7
⊢ (dom
(𝑓 ↾ ∪ 𝐷)
∩ dom (◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷))) ⊆ (∪ 𝐷
∩ dom (◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷))) | 
| 8 |   | dmres 4967 | 
. . . . . . . . 9
⊢ dom
(◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷)) = ((𝐴 ∖ ∪ 𝐷) ∩ dom ◡𝑔) | 
| 9 |   | inss1 3383 | 
. . . . . . . . 9
⊢ ((𝐴 ∖ ∪ 𝐷)
∩ dom ◡𝑔) ⊆ (𝐴 ∖ ∪ 𝐷) | 
| 10 | 8, 9 | eqsstri 3215 | 
. . . . . . . 8
⊢ dom
(◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷)) ⊆ (𝐴 ∖ ∪ 𝐷) | 
| 11 |   | sslin 3389 | 
. . . . . . . 8
⊢ (dom
(◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷)) ⊆ (𝐴 ∖ ∪ 𝐷) → (∪ 𝐷
∩ dom (◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷))) ⊆ (∪ 𝐷
∩ (𝐴 ∖ ∪ 𝐷))) | 
| 12 | 10, 11 | ax-mp 5 | 
. . . . . . 7
⊢ (∪ 𝐷
∩ dom (◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷))) ⊆ (∪ 𝐷
∩ (𝐴 ∖ ∪ 𝐷)) | 
| 13 | 7, 12 | sstri 3192 | 
. . . . . 6
⊢ (dom
(𝑓 ↾ ∪ 𝐷)
∩ dom (◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷))) ⊆ (∪ 𝐷
∩ (𝐴 ∖ ∪ 𝐷)) | 
| 14 |   | disjdif 3523 | 
. . . . . 6
⊢ (∪ 𝐷
∩ (𝐴 ∖ ∪ 𝐷))
= ∅ | 
| 15 | 13, 14 | sseqtri 3217 | 
. . . . 5
⊢ (dom
(𝑓 ↾ ∪ 𝐷)
∩ dom (◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷))) ⊆
∅ | 
| 16 |   | ss0 3491 | 
. . . . 5
⊢ ((dom
(𝑓 ↾ ∪ 𝐷)
∩ dom (◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷))) ⊆ ∅ → (dom
(𝑓 ↾ ∪ 𝐷)
∩ dom (◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷))) = ∅) | 
| 17 | 15, 16 | ax-mp 5 | 
. . . 4
⊢ (dom
(𝑓 ↾ ∪ 𝐷)
∩ dom (◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷))) = ∅ | 
| 18 |   | funun 5302 | 
. . . 4
⊢ (((Fun
(𝑓 ↾ ∪ 𝐷)
∧ Fun (◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷))) ∧ (dom (𝑓 ↾ ∪ 𝐷)
∩ dom (◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷))) = ∅) → Fun
((𝑓 ↾ ∪ 𝐷)
∪ (◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷)))) | 
| 19 | 17, 18 | mpan2 425 | 
. . 3
⊢ ((Fun
(𝑓 ↾ ∪ 𝐷)
∧ Fun (◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷))) → Fun ((𝑓 ↾ ∪ 𝐷)
∪ (◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷)))) | 
| 20 | 1, 2, 19 | syl2an 289 | 
. 2
⊢ ((Fun
𝑓 ∧ Fun ◡𝑔) → Fun ((𝑓 ↾ ∪ 𝐷) ∪ (◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷)))) | 
| 21 |   | sbthlem.3 | 
. . 3
⊢ 𝐻 = ((𝑓 ↾ ∪ 𝐷) ∪ (◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷))) | 
| 22 | 21 | funeqi 5279 | 
. 2
⊢ (Fun
𝐻 ↔ Fun ((𝑓 ↾ ∪ 𝐷)
∪ (◡𝑔 ↾ (𝐴 ∖ ∪ 𝐷)))) | 
| 23 | 20, 22 | sylibr 134 | 
1
⊢ ((Fun
𝑓 ∧ Fun ◡𝑔) → Fun 𝐻) |