Proof of Theorem elrabsf
| Step | Hyp | Ref
| Expression |
| 1 | | elrabsf.1 |
. . . 4
⊢ (y ∈ B → ∀x y ∈ B) |
| 2 | | ax-17 973 |
. . . 4
⊢ (y ∈ B → ∀z y ∈ B) |
| 3 | | ax-17 973 |
. . . 4
⊢ (φ → ∀zφ) |
| 4 | | hbs1 1334 |
. . . 4
⊢ ([z / x]φ → ∀x[z / x]φ) |
| 5 | | sbequ12 1183 |
. . . 4
⊢ (x = z →
(φ ↔ [z / x]φ)) |
| 6 | 1, 2, 3, 4, 5 | cbvrab 1913 |
. . 3
⊢ {x ∈ B∣φ} = {z
∈ B∣[z / x]φ} |
| 7 | 6 | eleq2i 1541 |
. 2
⊢ (A ∈ {x ∈ B∣φ} ↔ A ∈ {z ∈ B∣[z / x]φ}) |
| 8 | | ax-17 973 |
. . . 4
⊢ (w ∈ A → ∀z w ∈ A) |
| 9 | | ax-17 973 |
. . . 4
⊢ (w ∈ B → ∀z w ∈ B) |
| 10 | 8 | hbsbc1 1952 |
. . . 4
⊢ ((A ∈ V
→ [A / z][z / x]φ) →
∀z(A ∈ V → [A / z][z / x]φ)) |
| 11 | | sbceq1a 1947 |
. . . . 5
⊢ (z = A →
([z / x]φ ↔
[A / z][z / x]φ)) |
| 12 | | 19.8a 1031 |
. . . . . . 7
⊢ (z = A →
∃z
z = A) |
| 13 | | isset 1817 |
. . . . . . 7
⊢ (A ∈ V
↔ ∃z z = A) |
| 14 | 12, 13 | sylibr 200 |
. . . . . 6
⊢ (z = A →
A ∈
V) |
| 15 | | biimt 733 |
. . . . . 6
⊢ (A ∈ V
→ ([A / z][z / x]φ ↔
(A ∈
V → [A / z][z / x]φ))) |
| 16 | 14, 15 | syl 10 |
. . . . 5
⊢ (z = A →
([A / z][z / x]φ ↔
(A ∈
V → [A / z][z / x]φ))) |
| 17 | 11, 16 | bitrd 530 |
. . . 4
⊢ (z = A →
([z / x]φ ↔
(A ∈
V → [A / z][z / x]φ))) |
| 18 | 8, 9, 10, 17 | elrabf 1907 |
. . 3
⊢ (A ∈ {z ∈ B∣[z / x]φ} ↔ (A ∈ B ⋀ (A ∈ V
→ [A / z][z / x]φ))) |
| 19 | | elisset 1820 |
. . . . 5
⊢ (A ∈ B → A ∈ V) |
| 20 | 19, 15 | syl 10 |
. . . 4
⊢ (A ∈ B → ([A /
z][z /
x]φ
↔ (A ∈ V → [A / z][z / x]φ))) |
| 21 | 20 | pm5.32i 647 |
. . 3
⊢ ((A ∈ B ⋀ [A / z][z / x]φ) ↔ (A ∈ B ⋀ (A ∈ V
→ [A / z][z / x]φ))) |
| 22 | 18, 21 | bitr4 176 |
. 2
⊢ (A ∈ {z ∈ B∣[z / x]φ} ↔ (A ∈ B ⋀ [A / z][z / x]φ)) |
| 23 | | sbccog 1955 |
. . 3
⊢ (A ∈ B → ([A /
z][z /
x]φ
↔ [A / x]φ)) |
| 24 | 23 | pm5.32i 647 |
. 2
⊢ ((A ∈ B ⋀ [A / z][z / x]φ) ↔ (A ∈ B ⋀ [A / x]φ)) |
| 25 | 7, 22, 24 | 3bitr 177 |
1
⊢ (A ∈ {x ∈ B∣φ} ↔ (A ∈ B ⋀ [A / x]φ)) |