| Step | Hyp | Ref
 | Expression | 
| 1 |   | elinel2 3350 | 
. . . . . . . . 9
⊢ (𝑃 ∈ (𝑋 ∩ 𝑌) → 𝑃 ∈ 𝑌) | 
| 2 |   | blres.2 | 
. . . . . . . . . . 11
⊢ 𝐶 = (𝐷 ↾ (𝑌 × 𝑌)) | 
| 3 | 2 | oveqi 5935 | 
. . . . . . . . . 10
⊢ (𝑃𝐶𝑥) = (𝑃(𝐷 ↾ (𝑌 × 𝑌))𝑥) | 
| 4 |   | ovres 6063 | 
. . . . . . . . . 10
⊢ ((𝑃 ∈ 𝑌 ∧ 𝑥 ∈ 𝑌) → (𝑃(𝐷 ↾ (𝑌 × 𝑌))𝑥) = (𝑃𝐷𝑥)) | 
| 5 | 3, 4 | eqtrid 2241 | 
. . . . . . . . 9
⊢ ((𝑃 ∈ 𝑌 ∧ 𝑥 ∈ 𝑌) → (𝑃𝐶𝑥) = (𝑃𝐷𝑥)) | 
| 6 | 1, 5 | sylan 283 | 
. . . . . . . 8
⊢ ((𝑃 ∈ (𝑋 ∩ 𝑌) ∧ 𝑥 ∈ 𝑌) → (𝑃𝐶𝑥) = (𝑃𝐷𝑥)) | 
| 7 | 6 | breq1d 4043 | 
. . . . . . 7
⊢ ((𝑃 ∈ (𝑋 ∩ 𝑌) ∧ 𝑥 ∈ 𝑌) → ((𝑃𝐶𝑥) < 𝑅 ↔ (𝑃𝐷𝑥) < 𝑅)) | 
| 8 | 7 | anbi2d 464 | 
. . . . . 6
⊢ ((𝑃 ∈ (𝑋 ∩ 𝑌) ∧ 𝑥 ∈ 𝑌) → ((𝑥 ∈ 𝑋 ∧ (𝑃𝐶𝑥) < 𝑅) ↔ (𝑥 ∈ 𝑋 ∧ (𝑃𝐷𝑥) < 𝑅))) | 
| 9 | 8 | pm5.32da 452 | 
. . . . 5
⊢ (𝑃 ∈ (𝑋 ∩ 𝑌) → ((𝑥 ∈ 𝑌 ∧ (𝑥 ∈ 𝑋 ∧ (𝑃𝐶𝑥) < 𝑅)) ↔ (𝑥 ∈ 𝑌 ∧ (𝑥 ∈ 𝑋 ∧ (𝑃𝐷𝑥) < 𝑅)))) | 
| 10 | 9 | 3ad2ant2 1021 | 
. . . 4
⊢ ((𝐷 ∈ (∞Met‘𝑋) ∧ 𝑃 ∈ (𝑋 ∩ 𝑌) ∧ 𝑅 ∈ ℝ*) → ((𝑥 ∈ 𝑌 ∧ (𝑥 ∈ 𝑋 ∧ (𝑃𝐶𝑥) < 𝑅)) ↔ (𝑥 ∈ 𝑌 ∧ (𝑥 ∈ 𝑋 ∧ (𝑃𝐷𝑥) < 𝑅)))) | 
| 11 |   | elin 3346 | 
. . . . . . 7
⊢ (𝑥 ∈ (𝑋 ∩ 𝑌) ↔ (𝑥 ∈ 𝑋 ∧ 𝑥 ∈ 𝑌)) | 
| 12 |   | ancom 266 | 
. . . . . . 7
⊢ ((𝑥 ∈ 𝑋 ∧ 𝑥 ∈ 𝑌) ↔ (𝑥 ∈ 𝑌 ∧ 𝑥 ∈ 𝑋)) | 
| 13 | 11, 12 | bitri 184 | 
. . . . . 6
⊢ (𝑥 ∈ (𝑋 ∩ 𝑌) ↔ (𝑥 ∈ 𝑌 ∧ 𝑥 ∈ 𝑋)) | 
| 14 | 13 | anbi1i 458 | 
. . . . 5
⊢ ((𝑥 ∈ (𝑋 ∩ 𝑌) ∧ (𝑃𝐶𝑥) < 𝑅) ↔ ((𝑥 ∈ 𝑌 ∧ 𝑥 ∈ 𝑋) ∧ (𝑃𝐶𝑥) < 𝑅)) | 
| 15 |   | anass 401 | 
. . . . 5
⊢ (((𝑥 ∈ 𝑌 ∧ 𝑥 ∈ 𝑋) ∧ (𝑃𝐶𝑥) < 𝑅) ↔ (𝑥 ∈ 𝑌 ∧ (𝑥 ∈ 𝑋 ∧ (𝑃𝐶𝑥) < 𝑅))) | 
| 16 | 14, 15 | bitri 184 | 
. . . 4
⊢ ((𝑥 ∈ (𝑋 ∩ 𝑌) ∧ (𝑃𝐶𝑥) < 𝑅) ↔ (𝑥 ∈ 𝑌 ∧ (𝑥 ∈ 𝑋 ∧ (𝑃𝐶𝑥) < 𝑅))) | 
| 17 |   | ancom 266 | 
. . . 4
⊢ (((𝑥 ∈ 𝑋 ∧ (𝑃𝐷𝑥) < 𝑅) ∧ 𝑥 ∈ 𝑌) ↔ (𝑥 ∈ 𝑌 ∧ (𝑥 ∈ 𝑋 ∧ (𝑃𝐷𝑥) < 𝑅))) | 
| 18 | 10, 16, 17 | 3bitr4g 223 | 
. . 3
⊢ ((𝐷 ∈ (∞Met‘𝑋) ∧ 𝑃 ∈ (𝑋 ∩ 𝑌) ∧ 𝑅 ∈ ℝ*) → ((𝑥 ∈ (𝑋 ∩ 𝑌) ∧ (𝑃𝐶𝑥) < 𝑅) ↔ ((𝑥 ∈ 𝑋 ∧ (𝑃𝐷𝑥) < 𝑅) ∧ 𝑥 ∈ 𝑌))) | 
| 19 |   | xmetres 14618 | 
. . . . 5
⊢ (𝐷 ∈ (∞Met‘𝑋) → (𝐷 ↾ (𝑌 × 𝑌)) ∈ (∞Met‘(𝑋 ∩ 𝑌))) | 
| 20 | 2, 19 | eqeltrid 2283 | 
. . . 4
⊢ (𝐷 ∈ (∞Met‘𝑋) → 𝐶 ∈ (∞Met‘(𝑋 ∩ 𝑌))) | 
| 21 |   | elbl 14627 | 
. . . 4
⊢ ((𝐶 ∈ (∞Met‘(𝑋 ∩ 𝑌)) ∧ 𝑃 ∈ (𝑋 ∩ 𝑌) ∧ 𝑅 ∈ ℝ*) → (𝑥 ∈ (𝑃(ball‘𝐶)𝑅) ↔ (𝑥 ∈ (𝑋 ∩ 𝑌) ∧ (𝑃𝐶𝑥) < 𝑅))) | 
| 22 | 20, 21 | syl3an1 1282 | 
. . 3
⊢ ((𝐷 ∈ (∞Met‘𝑋) ∧ 𝑃 ∈ (𝑋 ∩ 𝑌) ∧ 𝑅 ∈ ℝ*) → (𝑥 ∈ (𝑃(ball‘𝐶)𝑅) ↔ (𝑥 ∈ (𝑋 ∩ 𝑌) ∧ (𝑃𝐶𝑥) < 𝑅))) | 
| 23 |   | elin 3346 | 
. . . 4
⊢ (𝑥 ∈ ((𝑃(ball‘𝐷)𝑅) ∩ 𝑌) ↔ (𝑥 ∈ (𝑃(ball‘𝐷)𝑅) ∧ 𝑥 ∈ 𝑌)) | 
| 24 |   | elinel1 3349 | 
. . . . . 6
⊢ (𝑃 ∈ (𝑋 ∩ 𝑌) → 𝑃 ∈ 𝑋) | 
| 25 |   | elbl 14627 | 
. . . . . 6
⊢ ((𝐷 ∈ (∞Met‘𝑋) ∧ 𝑃 ∈ 𝑋 ∧ 𝑅 ∈ ℝ*) → (𝑥 ∈ (𝑃(ball‘𝐷)𝑅) ↔ (𝑥 ∈ 𝑋 ∧ (𝑃𝐷𝑥) < 𝑅))) | 
| 26 | 24, 25 | syl3an2 1283 | 
. . . . 5
⊢ ((𝐷 ∈ (∞Met‘𝑋) ∧ 𝑃 ∈ (𝑋 ∩ 𝑌) ∧ 𝑅 ∈ ℝ*) → (𝑥 ∈ (𝑃(ball‘𝐷)𝑅) ↔ (𝑥 ∈ 𝑋 ∧ (𝑃𝐷𝑥) < 𝑅))) | 
| 27 | 26 | anbi1d 465 | 
. . . 4
⊢ ((𝐷 ∈ (∞Met‘𝑋) ∧ 𝑃 ∈ (𝑋 ∩ 𝑌) ∧ 𝑅 ∈ ℝ*) → ((𝑥 ∈ (𝑃(ball‘𝐷)𝑅) ∧ 𝑥 ∈ 𝑌) ↔ ((𝑥 ∈ 𝑋 ∧ (𝑃𝐷𝑥) < 𝑅) ∧ 𝑥 ∈ 𝑌))) | 
| 28 | 23, 27 | bitrid 192 | 
. . 3
⊢ ((𝐷 ∈ (∞Met‘𝑋) ∧ 𝑃 ∈ (𝑋 ∩ 𝑌) ∧ 𝑅 ∈ ℝ*) → (𝑥 ∈ ((𝑃(ball‘𝐷)𝑅) ∩ 𝑌) ↔ ((𝑥 ∈ 𝑋 ∧ (𝑃𝐷𝑥) < 𝑅) ∧ 𝑥 ∈ 𝑌))) | 
| 29 | 18, 22, 28 | 3bitr4d 220 | 
. 2
⊢ ((𝐷 ∈ (∞Met‘𝑋) ∧ 𝑃 ∈ (𝑋 ∩ 𝑌) ∧ 𝑅 ∈ ℝ*) → (𝑥 ∈ (𝑃(ball‘𝐶)𝑅) ↔ 𝑥 ∈ ((𝑃(ball‘𝐷)𝑅) ∩ 𝑌))) | 
| 30 | 29 | eqrdv 2194 | 
1
⊢ ((𝐷 ∈ (∞Met‘𝑋) ∧ 𝑃 ∈ (𝑋 ∩ 𝑌) ∧ 𝑅 ∈ ℝ*) → (𝑃(ball‘𝐶)𝑅) = ((𝑃(ball‘𝐷)𝑅) ∩ 𝑌)) |