| Step | Hyp | Ref
 | Expression | 
| 1 |   | f2ndres 6218 | 
. . 3
⊢
(2nd ↾ (𝑋 × 𝑌)):(𝑋 × 𝑌)⟶𝑌 | 
| 2 | 1 | a1i 9 | 
. 2
⊢ ((𝑅 ∈ (TopOn‘𝑋) ∧ 𝑆 ∈ (TopOn‘𝑌)) → (2nd ↾ (𝑋 × 𝑌)):(𝑋 × 𝑌)⟶𝑌) | 
| 3 |   | ffn 5407 | 
. . . . . . . 8
⊢
((2nd ↾ (𝑋 × 𝑌)):(𝑋 × 𝑌)⟶𝑌 → (2nd ↾ (𝑋 × 𝑌)) Fn (𝑋 × 𝑌)) | 
| 4 |   | elpreima 5681 | 
. . . . . . . 8
⊢
((2nd ↾ (𝑋 × 𝑌)) Fn (𝑋 × 𝑌) → (𝑧 ∈ (◡(2nd ↾ (𝑋 × 𝑌)) “ 𝑤) ↔ (𝑧 ∈ (𝑋 × 𝑌) ∧ ((2nd ↾ (𝑋 × 𝑌))‘𝑧) ∈ 𝑤))) | 
| 5 | 1, 3, 4 | mp2b 8 | 
. . . . . . 7
⊢ (𝑧 ∈ (◡(2nd ↾ (𝑋 × 𝑌)) “ 𝑤) ↔ (𝑧 ∈ (𝑋 × 𝑌) ∧ ((2nd ↾ (𝑋 × 𝑌))‘𝑧) ∈ 𝑤)) | 
| 6 |   | fvres 5582 | 
. . . . . . . . . 10
⊢ (𝑧 ∈ (𝑋 × 𝑌) → ((2nd ↾ (𝑋 × 𝑌))‘𝑧) = (2nd ‘𝑧)) | 
| 7 | 6 | eleq1d 2265 | 
. . . . . . . . 9
⊢ (𝑧 ∈ (𝑋 × 𝑌) → (((2nd ↾ (𝑋 × 𝑌))‘𝑧) ∈ 𝑤 ↔ (2nd ‘𝑧) ∈ 𝑤)) | 
| 8 |   | 1st2nd2 6233 | 
. . . . . . . . . 10
⊢ (𝑧 ∈ (𝑋 × 𝑌) → 𝑧 = 〈(1st ‘𝑧), (2nd ‘𝑧)〉) | 
| 9 |   | xp1st 6223 | 
. . . . . . . . . 10
⊢ (𝑧 ∈ (𝑋 × 𝑌) → (1st ‘𝑧) ∈ 𝑋) | 
| 10 |   | elxp6 6227 | 
. . . . . . . . . . . 12
⊢ (𝑧 ∈ (𝑋 × 𝑤) ↔ (𝑧 = 〈(1st ‘𝑧), (2nd ‘𝑧)〉 ∧ ((1st
‘𝑧) ∈ 𝑋 ∧ (2nd
‘𝑧) ∈ 𝑤))) | 
| 11 |   | anass 401 | 
. . . . . . . . . . . 12
⊢ (((𝑧 = 〈(1st
‘𝑧), (2nd
‘𝑧)〉 ∧
(1st ‘𝑧)
∈ 𝑋) ∧
(2nd ‘𝑧)
∈ 𝑤) ↔ (𝑧 = 〈(1st
‘𝑧), (2nd
‘𝑧)〉 ∧
((1st ‘𝑧)
∈ 𝑋 ∧
(2nd ‘𝑧)
∈ 𝑤))) | 
| 12 | 10, 11 | bitr4i 187 | 
. . . . . . . . . . 11
⊢ (𝑧 ∈ (𝑋 × 𝑤) ↔ ((𝑧 = 〈(1st ‘𝑧), (2nd ‘𝑧)〉 ∧ (1st
‘𝑧) ∈ 𝑋) ∧ (2nd
‘𝑧) ∈ 𝑤)) | 
| 13 | 12 | baib 920 | 
. . . . . . . . . 10
⊢ ((𝑧 = 〈(1st
‘𝑧), (2nd
‘𝑧)〉 ∧
(1st ‘𝑧)
∈ 𝑋) → (𝑧 ∈ (𝑋 × 𝑤) ↔ (2nd ‘𝑧) ∈ 𝑤)) | 
| 14 | 8, 9, 13 | syl2anc 411 | 
. . . . . . . . 9
⊢ (𝑧 ∈ (𝑋 × 𝑌) → (𝑧 ∈ (𝑋 × 𝑤) ↔ (2nd ‘𝑧) ∈ 𝑤)) | 
| 15 | 7, 14 | bitr4d 191 | 
. . . . . . . 8
⊢ (𝑧 ∈ (𝑋 × 𝑌) → (((2nd ↾ (𝑋 × 𝑌))‘𝑧) ∈ 𝑤 ↔ 𝑧 ∈ (𝑋 × 𝑤))) | 
| 16 | 15 | pm5.32i 454 | 
. . . . . . 7
⊢ ((𝑧 ∈ (𝑋 × 𝑌) ∧ ((2nd ↾ (𝑋 × 𝑌))‘𝑧) ∈ 𝑤) ↔ (𝑧 ∈ (𝑋 × 𝑌) ∧ 𝑧 ∈ (𝑋 × 𝑤))) | 
| 17 | 5, 16 | bitri 184 | 
. . . . . 6
⊢ (𝑧 ∈ (◡(2nd ↾ (𝑋 × 𝑌)) “ 𝑤) ↔ (𝑧 ∈ (𝑋 × 𝑌) ∧ 𝑧 ∈ (𝑋 × 𝑤))) | 
| 18 |   | toponss 14262 | 
. . . . . . . . . 10
⊢ ((𝑆 ∈ (TopOn‘𝑌) ∧ 𝑤 ∈ 𝑆) → 𝑤 ⊆ 𝑌) | 
| 19 | 18 | adantll 476 | 
. . . . . . . . 9
⊢ (((𝑅 ∈ (TopOn‘𝑋) ∧ 𝑆 ∈ (TopOn‘𝑌)) ∧ 𝑤 ∈ 𝑆) → 𝑤 ⊆ 𝑌) | 
| 20 |   | xpss2 4774 | 
. . . . . . . . 9
⊢ (𝑤 ⊆ 𝑌 → (𝑋 × 𝑤) ⊆ (𝑋 × 𝑌)) | 
| 21 | 19, 20 | syl 14 | 
. . . . . . . 8
⊢ (((𝑅 ∈ (TopOn‘𝑋) ∧ 𝑆 ∈ (TopOn‘𝑌)) ∧ 𝑤 ∈ 𝑆) → (𝑋 × 𝑤) ⊆ (𝑋 × 𝑌)) | 
| 22 | 21 | sseld 3182 | 
. . . . . . 7
⊢ (((𝑅 ∈ (TopOn‘𝑋) ∧ 𝑆 ∈ (TopOn‘𝑌)) ∧ 𝑤 ∈ 𝑆) → (𝑧 ∈ (𝑋 × 𝑤) → 𝑧 ∈ (𝑋 × 𝑌))) | 
| 23 | 22 | pm4.71rd 394 | 
. . . . . 6
⊢ (((𝑅 ∈ (TopOn‘𝑋) ∧ 𝑆 ∈ (TopOn‘𝑌)) ∧ 𝑤 ∈ 𝑆) → (𝑧 ∈ (𝑋 × 𝑤) ↔ (𝑧 ∈ (𝑋 × 𝑌) ∧ 𝑧 ∈ (𝑋 × 𝑤)))) | 
| 24 | 17, 23 | bitr4id 199 | 
. . . . 5
⊢ (((𝑅 ∈ (TopOn‘𝑋) ∧ 𝑆 ∈ (TopOn‘𝑌)) ∧ 𝑤 ∈ 𝑆) → (𝑧 ∈ (◡(2nd ↾ (𝑋 × 𝑌)) “ 𝑤) ↔ 𝑧 ∈ (𝑋 × 𝑤))) | 
| 25 | 24 | eqrdv 2194 | 
. . . 4
⊢ (((𝑅 ∈ (TopOn‘𝑋) ∧ 𝑆 ∈ (TopOn‘𝑌)) ∧ 𝑤 ∈ 𝑆) → (◡(2nd ↾ (𝑋 × 𝑌)) “ 𝑤) = (𝑋 × 𝑤)) | 
| 26 |   | toponmax 14261 | 
. . . . . 6
⊢ (𝑅 ∈ (TopOn‘𝑋) → 𝑋 ∈ 𝑅) | 
| 27 |   | txopn 14501 | 
. . . . . . 7
⊢ (((𝑅 ∈ (TopOn‘𝑋) ∧ 𝑆 ∈ (TopOn‘𝑌)) ∧ (𝑋 ∈ 𝑅 ∧ 𝑤 ∈ 𝑆)) → (𝑋 × 𝑤) ∈ (𝑅 ×t 𝑆)) | 
| 28 | 27 | expr 375 | 
. . . . . 6
⊢ (((𝑅 ∈ (TopOn‘𝑋) ∧ 𝑆 ∈ (TopOn‘𝑌)) ∧ 𝑋 ∈ 𝑅) → (𝑤 ∈ 𝑆 → (𝑋 × 𝑤) ∈ (𝑅 ×t 𝑆))) | 
| 29 | 26, 28 | mpidan 423 | 
. . . . 5
⊢ ((𝑅 ∈ (TopOn‘𝑋) ∧ 𝑆 ∈ (TopOn‘𝑌)) → (𝑤 ∈ 𝑆 → (𝑋 × 𝑤) ∈ (𝑅 ×t 𝑆))) | 
| 30 | 29 | imp 124 | 
. . . 4
⊢ (((𝑅 ∈ (TopOn‘𝑋) ∧ 𝑆 ∈ (TopOn‘𝑌)) ∧ 𝑤 ∈ 𝑆) → (𝑋 × 𝑤) ∈ (𝑅 ×t 𝑆)) | 
| 31 | 25, 30 | eqeltrd 2273 | 
. . 3
⊢ (((𝑅 ∈ (TopOn‘𝑋) ∧ 𝑆 ∈ (TopOn‘𝑌)) ∧ 𝑤 ∈ 𝑆) → (◡(2nd ↾ (𝑋 × 𝑌)) “ 𝑤) ∈ (𝑅 ×t 𝑆)) | 
| 32 | 31 | ralrimiva 2570 | 
. 2
⊢ ((𝑅 ∈ (TopOn‘𝑋) ∧ 𝑆 ∈ (TopOn‘𝑌)) → ∀𝑤 ∈ 𝑆 (◡(2nd ↾ (𝑋 × 𝑌)) “ 𝑤) ∈ (𝑅 ×t 𝑆)) | 
| 33 |   | txtopon 14498 | 
. . 3
⊢ ((𝑅 ∈ (TopOn‘𝑋) ∧ 𝑆 ∈ (TopOn‘𝑌)) → (𝑅 ×t 𝑆) ∈ (TopOn‘(𝑋 × 𝑌))) | 
| 34 |   | iscn 14433 | 
. . 3
⊢ (((𝑅 ×t 𝑆) ∈ (TopOn‘(𝑋 × 𝑌)) ∧ 𝑆 ∈ (TopOn‘𝑌)) → ((2nd ↾ (𝑋 × 𝑌)) ∈ ((𝑅 ×t 𝑆) Cn 𝑆) ↔ ((2nd ↾ (𝑋 × 𝑌)):(𝑋 × 𝑌)⟶𝑌 ∧ ∀𝑤 ∈ 𝑆 (◡(2nd ↾ (𝑋 × 𝑌)) “ 𝑤) ∈ (𝑅 ×t 𝑆)))) | 
| 35 | 33, 34 | sylancom 420 | 
. 2
⊢ ((𝑅 ∈ (TopOn‘𝑋) ∧ 𝑆 ∈ (TopOn‘𝑌)) → ((2nd ↾ (𝑋 × 𝑌)) ∈ ((𝑅 ×t 𝑆) Cn 𝑆) ↔ ((2nd ↾ (𝑋 × 𝑌)):(𝑋 × 𝑌)⟶𝑌 ∧ ∀𝑤 ∈ 𝑆 (◡(2nd ↾ (𝑋 × 𝑌)) “ 𝑤) ∈ (𝑅 ×t 𝑆)))) | 
| 36 | 2, 32, 35 | mpbir2and 946 | 
1
⊢ ((𝑅 ∈ (TopOn‘𝑋) ∧ 𝑆 ∈ (TopOn‘𝑌)) → (2nd ↾ (𝑋 × 𝑌)) ∈ ((𝑅 ×t 𝑆) Cn 𝑆)) |