| Step | Hyp | Ref
 | Expression | 
| 1 |   | inss2 3384 | 
. . . 4
⊢ (𝑅 ∩ (𝐵 × 𝐵)) ⊆ (𝐵 × 𝐵) | 
| 2 |   | relxp 4772 | 
. . . 4
⊢ Rel
(𝐵 × 𝐵) | 
| 3 |   | relss 4750 | 
. . . 4
⊢ ((𝑅 ∩ (𝐵 × 𝐵)) ⊆ (𝐵 × 𝐵) → (Rel (𝐵 × 𝐵) → Rel (𝑅 ∩ (𝐵 × 𝐵)))) | 
| 4 | 1, 2, 3 | mp2 16 | 
. . 3
⊢ Rel
(𝑅 ∩ (𝐵 × 𝐵)) | 
| 5 | 4 | a1i 9 | 
. 2
⊢ (𝜑 → Rel (𝑅 ∩ (𝐵 × 𝐵))) | 
| 6 |   | simpr 110 | 
. . . . 5
⊢ ((𝜑 ∧ 𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑦) → 𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑦) | 
| 7 |   | brinxp2 4730 | 
. . . . 5
⊢ (𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑦 ↔ (𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵 ∧ 𝑥𝑅𝑦)) | 
| 8 | 6, 7 | sylib 122 | 
. . . 4
⊢ ((𝜑 ∧ 𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑦) → (𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵 ∧ 𝑥𝑅𝑦)) | 
| 9 | 8 | simp2d 1012 | 
. . 3
⊢ ((𝜑 ∧ 𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑦) → 𝑦 ∈ 𝐵) | 
| 10 | 8 | simp1d 1011 | 
. . 3
⊢ ((𝜑 ∧ 𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑦) → 𝑥 ∈ 𝐵) | 
| 11 |   | erinxp.r | 
. . . . 5
⊢ (𝜑 → 𝑅 Er 𝐴) | 
| 12 | 11 | adantr 276 | 
. . . 4
⊢ ((𝜑 ∧ 𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑦) → 𝑅 Er 𝐴) | 
| 13 | 8 | simp3d 1013 | 
. . . 4
⊢ ((𝜑 ∧ 𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑦) → 𝑥𝑅𝑦) | 
| 14 | 12, 13 | ersym 6604 | 
. . 3
⊢ ((𝜑 ∧ 𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑦) → 𝑦𝑅𝑥) | 
| 15 |   | brinxp2 4730 | 
. . 3
⊢ (𝑦(𝑅 ∩ (𝐵 × 𝐵))𝑥 ↔ (𝑦 ∈ 𝐵 ∧ 𝑥 ∈ 𝐵 ∧ 𝑦𝑅𝑥)) | 
| 16 | 9, 10, 14, 15 | syl3anbrc 1183 | 
. 2
⊢ ((𝜑 ∧ 𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑦) → 𝑦(𝑅 ∩ (𝐵 × 𝐵))𝑥) | 
| 17 | 10 | adantrr 479 | 
. . 3
⊢ ((𝜑 ∧ (𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑦 ∧ 𝑦(𝑅 ∩ (𝐵 × 𝐵))𝑧)) → 𝑥 ∈ 𝐵) | 
| 18 |   | simprr 531 | 
. . . . 5
⊢ ((𝜑 ∧ (𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑦 ∧ 𝑦(𝑅 ∩ (𝐵 × 𝐵))𝑧)) → 𝑦(𝑅 ∩ (𝐵 × 𝐵))𝑧) | 
| 19 |   | brinxp2 4730 | 
. . . . 5
⊢ (𝑦(𝑅 ∩ (𝐵 × 𝐵))𝑧 ↔ (𝑦 ∈ 𝐵 ∧ 𝑧 ∈ 𝐵 ∧ 𝑦𝑅𝑧)) | 
| 20 | 18, 19 | sylib 122 | 
. . . 4
⊢ ((𝜑 ∧ (𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑦 ∧ 𝑦(𝑅 ∩ (𝐵 × 𝐵))𝑧)) → (𝑦 ∈ 𝐵 ∧ 𝑧 ∈ 𝐵 ∧ 𝑦𝑅𝑧)) | 
| 21 | 20 | simp2d 1012 | 
. . 3
⊢ ((𝜑 ∧ (𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑦 ∧ 𝑦(𝑅 ∩ (𝐵 × 𝐵))𝑧)) → 𝑧 ∈ 𝐵) | 
| 22 | 11 | adantr 276 | 
. . . 4
⊢ ((𝜑 ∧ (𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑦 ∧ 𝑦(𝑅 ∩ (𝐵 × 𝐵))𝑧)) → 𝑅 Er 𝐴) | 
| 23 | 13 | adantrr 479 | 
. . . 4
⊢ ((𝜑 ∧ (𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑦 ∧ 𝑦(𝑅 ∩ (𝐵 × 𝐵))𝑧)) → 𝑥𝑅𝑦) | 
| 24 | 20 | simp3d 1013 | 
. . . 4
⊢ ((𝜑 ∧ (𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑦 ∧ 𝑦(𝑅 ∩ (𝐵 × 𝐵))𝑧)) → 𝑦𝑅𝑧) | 
| 25 | 22, 23, 24 | ertrd 6608 | 
. . 3
⊢ ((𝜑 ∧ (𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑦 ∧ 𝑦(𝑅 ∩ (𝐵 × 𝐵))𝑧)) → 𝑥𝑅𝑧) | 
| 26 |   | brinxp2 4730 | 
. . 3
⊢ (𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑧 ↔ (𝑥 ∈ 𝐵 ∧ 𝑧 ∈ 𝐵 ∧ 𝑥𝑅𝑧)) | 
| 27 | 17, 21, 25, 26 | syl3anbrc 1183 | 
. 2
⊢ ((𝜑 ∧ (𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑦 ∧ 𝑦(𝑅 ∩ (𝐵 × 𝐵))𝑧)) → 𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑧) | 
| 28 | 11 | adantr 276 | 
. . . . . 6
⊢ ((𝜑 ∧ 𝑥 ∈ 𝐵) → 𝑅 Er 𝐴) | 
| 29 |   | erinxp.a | 
. . . . . . 7
⊢ (𝜑 → 𝐵 ⊆ 𝐴) | 
| 30 | 29 | sselda 3183 | 
. . . . . 6
⊢ ((𝜑 ∧ 𝑥 ∈ 𝐵) → 𝑥 ∈ 𝐴) | 
| 31 | 28, 30 | erref 6612 | 
. . . . 5
⊢ ((𝜑 ∧ 𝑥 ∈ 𝐵) → 𝑥𝑅𝑥) | 
| 32 | 31 | ex 115 | 
. . . 4
⊢ (𝜑 → (𝑥 ∈ 𝐵 → 𝑥𝑅𝑥)) | 
| 33 | 32 | pm4.71rd 394 | 
. . 3
⊢ (𝜑 → (𝑥 ∈ 𝐵 ↔ (𝑥𝑅𝑥 ∧ 𝑥 ∈ 𝐵))) | 
| 34 |   | brin 4085 | 
. . . 4
⊢ (𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑥 ↔ (𝑥𝑅𝑥 ∧ 𝑥(𝐵 × 𝐵)𝑥)) | 
| 35 |   | brxp 4694 | 
. . . . . 6
⊢ (𝑥(𝐵 × 𝐵)𝑥 ↔ (𝑥 ∈ 𝐵 ∧ 𝑥 ∈ 𝐵)) | 
| 36 |   | anidm 396 | 
. . . . . 6
⊢ ((𝑥 ∈ 𝐵 ∧ 𝑥 ∈ 𝐵) ↔ 𝑥 ∈ 𝐵) | 
| 37 | 35, 36 | bitri 184 | 
. . . . 5
⊢ (𝑥(𝐵 × 𝐵)𝑥 ↔ 𝑥 ∈ 𝐵) | 
| 38 | 37 | anbi2i 457 | 
. . . 4
⊢ ((𝑥𝑅𝑥 ∧ 𝑥(𝐵 × 𝐵)𝑥) ↔ (𝑥𝑅𝑥 ∧ 𝑥 ∈ 𝐵)) | 
| 39 | 34, 38 | bitri 184 | 
. . 3
⊢ (𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑥 ↔ (𝑥𝑅𝑥 ∧ 𝑥 ∈ 𝐵)) | 
| 40 | 33, 39 | bitr4di 198 | 
. 2
⊢ (𝜑 → (𝑥 ∈ 𝐵 ↔ 𝑥(𝑅 ∩ (𝐵 × 𝐵))𝑥)) | 
| 41 | 5, 16, 27, 40 | iserd 6618 | 
1
⊢ (𝜑 → (𝑅 ∩ (𝐵 × 𝐵)) Er 𝐵) |