| Step | Hyp | Ref
 | Expression | 
| 1 |   | relxp 4772 | 
. . . . . 6
⊢ Rel
(𝐶 × 𝐵) | 
| 2 | 1 | rgenw 2552 | 
. . . . 5
⊢
∀𝑥 ∈
𝐴 Rel (𝐶 × 𝐵) | 
| 3 |   | r19.2m 3537 | 
. . . . 5
⊢
((∃𝑦 𝑦 ∈ 𝐴 ∧ ∀𝑥 ∈ 𝐴 Rel (𝐶 × 𝐵)) → ∃𝑥 ∈ 𝐴 Rel (𝐶 × 𝐵)) | 
| 4 | 2, 3 | mpan2 425 | 
. . . 4
⊢
(∃𝑦 𝑦 ∈ 𝐴 → ∃𝑥 ∈ 𝐴 Rel (𝐶 × 𝐵)) | 
| 5 |   | reliin 4785 | 
. . . 4
⊢
(∃𝑥 ∈
𝐴 Rel (𝐶 × 𝐵) → Rel ∩ 𝑥 ∈ 𝐴 (𝐶 × 𝐵)) | 
| 6 | 4, 5 | syl 14 | 
. . 3
⊢
(∃𝑦 𝑦 ∈ 𝐴 → Rel ∩ 𝑥 ∈ 𝐴 (𝐶 × 𝐵)) | 
| 7 |   | relxp 4772 | 
. . 3
⊢ Rel
(𝐶 × ∩ 𝑥 ∈ 𝐴 𝐵) | 
| 8 | 6, 7 | jctil 312 | 
. 2
⊢
(∃𝑦 𝑦 ∈ 𝐴 → (Rel (𝐶 × ∩
𝑥 ∈ 𝐴 𝐵) ∧ Rel ∩ 𝑥 ∈ 𝐴 (𝐶 × 𝐵))) | 
| 9 |   | eleq1w 2257 | 
. . . . . . . 8
⊢ (𝑥 = 𝑦 → (𝑥 ∈ 𝐴 ↔ 𝑦 ∈ 𝐴)) | 
| 10 | 9 | cbvexv 1933 | 
. . . . . . 7
⊢
(∃𝑥 𝑥 ∈ 𝐴 ↔ ∃𝑦 𝑦 ∈ 𝐴) | 
| 11 |   | r19.28mv 3543 | 
. . . . . . 7
⊢
(∃𝑥 𝑥 ∈ 𝐴 → (∀𝑥 ∈ 𝐴 (𝑤 ∈ 𝐶 ∧ 𝑧 ∈ 𝐵) ↔ (𝑤 ∈ 𝐶 ∧ ∀𝑥 ∈ 𝐴 𝑧 ∈ 𝐵))) | 
| 12 | 10, 11 | sylbir 135 | 
. . . . . 6
⊢
(∃𝑦 𝑦 ∈ 𝐴 → (∀𝑥 ∈ 𝐴 (𝑤 ∈ 𝐶 ∧ 𝑧 ∈ 𝐵) ↔ (𝑤 ∈ 𝐶 ∧ ∀𝑥 ∈ 𝐴 𝑧 ∈ 𝐵))) | 
| 13 | 12 | bicomd 141 | 
. . . . 5
⊢
(∃𝑦 𝑦 ∈ 𝐴 → ((𝑤 ∈ 𝐶 ∧ ∀𝑥 ∈ 𝐴 𝑧 ∈ 𝐵) ↔ ∀𝑥 ∈ 𝐴 (𝑤 ∈ 𝐶 ∧ 𝑧 ∈ 𝐵))) | 
| 14 |   | eliin 3921 | 
. . . . . . 7
⊢ (𝑧 ∈ V → (𝑧 ∈ ∩ 𝑥 ∈ 𝐴 𝐵 ↔ ∀𝑥 ∈ 𝐴 𝑧 ∈ 𝐵)) | 
| 15 | 14 | elv 2767 | 
. . . . . 6
⊢ (𝑧 ∈ ∩ 𝑥 ∈ 𝐴 𝐵 ↔ ∀𝑥 ∈ 𝐴 𝑧 ∈ 𝐵) | 
| 16 | 15 | anbi2i 457 | 
. . . . 5
⊢ ((𝑤 ∈ 𝐶 ∧ 𝑧 ∈ ∩
𝑥 ∈ 𝐴 𝐵) ↔ (𝑤 ∈ 𝐶 ∧ ∀𝑥 ∈ 𝐴 𝑧 ∈ 𝐵)) | 
| 17 |   | opelxp 4693 | 
. . . . . 6
⊢
(〈𝑤, 𝑧〉 ∈ (𝐶 × 𝐵) ↔ (𝑤 ∈ 𝐶 ∧ 𝑧 ∈ 𝐵)) | 
| 18 | 17 | ralbii 2503 | 
. . . . 5
⊢
(∀𝑥 ∈
𝐴 〈𝑤, 𝑧〉 ∈ (𝐶 × 𝐵) ↔ ∀𝑥 ∈ 𝐴 (𝑤 ∈ 𝐶 ∧ 𝑧 ∈ 𝐵)) | 
| 19 | 13, 16, 18 | 3bitr4g 223 | 
. . . 4
⊢
(∃𝑦 𝑦 ∈ 𝐴 → ((𝑤 ∈ 𝐶 ∧ 𝑧 ∈ ∩
𝑥 ∈ 𝐴 𝐵) ↔ ∀𝑥 ∈ 𝐴 〈𝑤, 𝑧〉 ∈ (𝐶 × 𝐵))) | 
| 20 |   | opelxp 4693 | 
. . . 4
⊢
(〈𝑤, 𝑧〉 ∈ (𝐶 × ∩
𝑥 ∈ 𝐴 𝐵) ↔ (𝑤 ∈ 𝐶 ∧ 𝑧 ∈ ∩
𝑥 ∈ 𝐴 𝐵)) | 
| 21 |   | vex 2766 | 
. . . . . 6
⊢ 𝑤 ∈ V | 
| 22 |   | vex 2766 | 
. . . . . 6
⊢ 𝑧 ∈ V | 
| 23 | 21, 22 | opex 4262 | 
. . . . 5
⊢
〈𝑤, 𝑧〉 ∈ V | 
| 24 |   | eliin 3921 | 
. . . . 5
⊢
(〈𝑤, 𝑧〉 ∈ V →
(〈𝑤, 𝑧〉 ∈ ∩ 𝑥 ∈ 𝐴 (𝐶 × 𝐵) ↔ ∀𝑥 ∈ 𝐴 〈𝑤, 𝑧〉 ∈ (𝐶 × 𝐵))) | 
| 25 | 23, 24 | ax-mp 5 | 
. . . 4
⊢
(〈𝑤, 𝑧〉 ∈ ∩ 𝑥 ∈ 𝐴 (𝐶 × 𝐵) ↔ ∀𝑥 ∈ 𝐴 〈𝑤, 𝑧〉 ∈ (𝐶 × 𝐵)) | 
| 26 | 19, 20, 25 | 3bitr4g 223 | 
. . 3
⊢
(∃𝑦 𝑦 ∈ 𝐴 → (〈𝑤, 𝑧〉 ∈ (𝐶 × ∩
𝑥 ∈ 𝐴 𝐵) ↔ 〈𝑤, 𝑧〉 ∈ ∩ 𝑥 ∈ 𝐴 (𝐶 × 𝐵))) | 
| 27 | 26 | eqrelrdv2 4762 | 
. 2
⊢ (((Rel
(𝐶 × ∩ 𝑥 ∈ 𝐴 𝐵) ∧ Rel ∩ 𝑥 ∈ 𝐴 (𝐶 × 𝐵)) ∧ ∃𝑦 𝑦 ∈ 𝐴) → (𝐶 × ∩
𝑥 ∈ 𝐴 𝐵) = ∩
𝑥 ∈ 𝐴 (𝐶 × 𝐵)) | 
| 28 | 8, 27 | mpancom 422 | 
1
⊢
(∃𝑦 𝑦 ∈ 𝐴 → (𝐶 × ∩
𝑥 ∈ 𝐴 𝐵) = ∩
𝑥 ∈ 𝐴 (𝐶 × 𝐵)) |