Proof of Theorem csbiebt
| Step | Hyp | Ref
 | Expression | 
| 1 |   | elex 2774 | 
. 2
⊢ (𝐴 ∈ 𝑉 → 𝐴 ∈ V) | 
| 2 |   | spsbc 3001 | 
. . . . 5
⊢ (𝐴 ∈ V → (∀𝑥(𝑥 = 𝐴 → 𝐵 = 𝐶) → [𝐴 / 𝑥](𝑥 = 𝐴 → 𝐵 = 𝐶))) | 
| 3 | 2 | adantr 276 | 
. . . 4
⊢ ((𝐴 ∈ V ∧
Ⅎ𝑥𝐶) → (∀𝑥(𝑥 = 𝐴 → 𝐵 = 𝐶) → [𝐴 / 𝑥](𝑥 = 𝐴 → 𝐵 = 𝐶))) | 
| 4 |   | simpl 109 | 
. . . . 5
⊢ ((𝐴 ∈ V ∧
Ⅎ𝑥𝐶) → 𝐴 ∈ V) | 
| 5 |   | biimt 241 | 
. . . . . . 7
⊢ (𝑥 = 𝐴 → (𝐵 = 𝐶 ↔ (𝑥 = 𝐴 → 𝐵 = 𝐶))) | 
| 6 |   | csbeq1a 3093 | 
. . . . . . . 8
⊢ (𝑥 = 𝐴 → 𝐵 = ⦋𝐴 / 𝑥⦌𝐵) | 
| 7 | 6 | eqeq1d 2205 | 
. . . . . . 7
⊢ (𝑥 = 𝐴 → (𝐵 = 𝐶 ↔ ⦋𝐴 / 𝑥⦌𝐵 = 𝐶)) | 
| 8 | 5, 7 | bitr3d 190 | 
. . . . . 6
⊢ (𝑥 = 𝐴 → ((𝑥 = 𝐴 → 𝐵 = 𝐶) ↔ ⦋𝐴 / 𝑥⦌𝐵 = 𝐶)) | 
| 9 | 8 | adantl 277 | 
. . . . 5
⊢ (((𝐴 ∈ V ∧
Ⅎ𝑥𝐶) ∧ 𝑥 = 𝐴) → ((𝑥 = 𝐴 → 𝐵 = 𝐶) ↔ ⦋𝐴 / 𝑥⦌𝐵 = 𝐶)) | 
| 10 |   | nfv 1542 | 
. . . . . 6
⊢
Ⅎ𝑥 𝐴 ∈ V | 
| 11 |   | nfnfc1 2342 | 
. . . . . 6
⊢
Ⅎ𝑥Ⅎ𝑥𝐶 | 
| 12 | 10, 11 | nfan 1579 | 
. . . . 5
⊢
Ⅎ𝑥(𝐴 ∈ V ∧
Ⅎ𝑥𝐶) | 
| 13 |   | nfcsb1v 3117 | 
. . . . . . 7
⊢
Ⅎ𝑥⦋𝐴 / 𝑥⦌𝐵 | 
| 14 | 13 | a1i 9 | 
. . . . . 6
⊢ ((𝐴 ∈ V ∧
Ⅎ𝑥𝐶) → Ⅎ𝑥⦋𝐴 / 𝑥⦌𝐵) | 
| 15 |   | simpr 110 | 
. . . . . 6
⊢ ((𝐴 ∈ V ∧
Ⅎ𝑥𝐶) → Ⅎ𝑥𝐶) | 
| 16 | 14, 15 | nfeqd 2354 | 
. . . . 5
⊢ ((𝐴 ∈ V ∧
Ⅎ𝑥𝐶) → Ⅎ𝑥⦋𝐴 / 𝑥⦌𝐵 = 𝐶) | 
| 17 | 4, 9, 12, 16 | sbciedf 3025 | 
. . . 4
⊢ ((𝐴 ∈ V ∧
Ⅎ𝑥𝐶) → ([𝐴 / 𝑥](𝑥 = 𝐴 → 𝐵 = 𝐶) ↔ ⦋𝐴 / 𝑥⦌𝐵 = 𝐶)) | 
| 18 | 3, 17 | sylibd 149 | 
. . 3
⊢ ((𝐴 ∈ V ∧
Ⅎ𝑥𝐶) → (∀𝑥(𝑥 = 𝐴 → 𝐵 = 𝐶) → ⦋𝐴 / 𝑥⦌𝐵 = 𝐶)) | 
| 19 | 13 | a1i 9 | 
. . . . . . . 8
⊢
(Ⅎ𝑥𝐶 → Ⅎ𝑥⦋𝐴 / 𝑥⦌𝐵) | 
| 20 |   | id 19 | 
. . . . . . . 8
⊢
(Ⅎ𝑥𝐶 → Ⅎ𝑥𝐶) | 
| 21 | 19, 20 | nfeqd 2354 | 
. . . . . . 7
⊢
(Ⅎ𝑥𝐶 → Ⅎ𝑥⦋𝐴 / 𝑥⦌𝐵 = 𝐶) | 
| 22 | 11, 21 | nfan1 1578 | 
. . . . . 6
⊢
Ⅎ𝑥(Ⅎ𝑥𝐶 ∧ ⦋𝐴 / 𝑥⦌𝐵 = 𝐶) | 
| 23 | 7 | biimprcd 160 | 
. . . . . . 7
⊢
(⦋𝐴 /
𝑥⦌𝐵 = 𝐶 → (𝑥 = 𝐴 → 𝐵 = 𝐶)) | 
| 24 | 23 | adantl 277 | 
. . . . . 6
⊢
((Ⅎ𝑥𝐶 ∧ ⦋𝐴 / 𝑥⦌𝐵 = 𝐶) → (𝑥 = 𝐴 → 𝐵 = 𝐶)) | 
| 25 | 22, 24 | alrimi 1536 | 
. . . . 5
⊢
((Ⅎ𝑥𝐶 ∧ ⦋𝐴 / 𝑥⦌𝐵 = 𝐶) → ∀𝑥(𝑥 = 𝐴 → 𝐵 = 𝐶)) | 
| 26 | 25 | ex 115 | 
. . . 4
⊢
(Ⅎ𝑥𝐶 → (⦋𝐴 / 𝑥⦌𝐵 = 𝐶 → ∀𝑥(𝑥 = 𝐴 → 𝐵 = 𝐶))) | 
| 27 | 26 | adantl 277 | 
. . 3
⊢ ((𝐴 ∈ V ∧
Ⅎ𝑥𝐶) → (⦋𝐴 / 𝑥⦌𝐵 = 𝐶 → ∀𝑥(𝑥 = 𝐴 → 𝐵 = 𝐶))) | 
| 28 | 18, 27 | impbid 129 | 
. 2
⊢ ((𝐴 ∈ V ∧
Ⅎ𝑥𝐶) → (∀𝑥(𝑥 = 𝐴 → 𝐵 = 𝐶) ↔ ⦋𝐴 / 𝑥⦌𝐵 = 𝐶)) | 
| 29 | 1, 28 | sylan 283 | 
1
⊢ ((𝐴 ∈ 𝑉 ∧ Ⅎ𝑥𝐶) → (∀𝑥(𝑥 = 𝐴 → 𝐵 = 𝐶) ↔ ⦋𝐴 / 𝑥⦌𝐵 = 𝐶)) |