Step |
Hyp |
Ref |
Expression |
1 |
|
bj-nfcf.nf |
⊢ Ⅎ 𝑦 𝐴 |
2 |
|
df-nfc |
⊢ ( Ⅎ 𝑥 𝐴 ↔ ∀ 𝑧 Ⅎ 𝑥 𝑧 ∈ 𝐴 ) |
3 |
1
|
nfcri |
⊢ Ⅎ 𝑦 𝑧 ∈ 𝐴 |
4 |
3
|
nfnf |
⊢ Ⅎ 𝑦 Ⅎ 𝑥 𝑧 ∈ 𝐴 |
5 |
4
|
sb8v |
⊢ ( ∀ 𝑧 Ⅎ 𝑥 𝑧 ∈ 𝐴 ↔ ∀ 𝑦 [ 𝑦 / 𝑧 ] Ⅎ 𝑥 𝑧 ∈ 𝐴 ) |
6 |
|
bj-sbnf |
⊢ ( [ 𝑦 / 𝑧 ] Ⅎ 𝑥 𝑧 ∈ 𝐴 ↔ Ⅎ 𝑥 [ 𝑦 / 𝑧 ] 𝑧 ∈ 𝐴 ) |
7 |
|
clelsb1 |
⊢ ( [ 𝑦 / 𝑧 ] 𝑧 ∈ 𝐴 ↔ 𝑦 ∈ 𝐴 ) |
8 |
7
|
nfbii |
⊢ ( Ⅎ 𝑥 [ 𝑦 / 𝑧 ] 𝑧 ∈ 𝐴 ↔ Ⅎ 𝑥 𝑦 ∈ 𝐴 ) |
9 |
6 8
|
bitri |
⊢ ( [ 𝑦 / 𝑧 ] Ⅎ 𝑥 𝑧 ∈ 𝐴 ↔ Ⅎ 𝑥 𝑦 ∈ 𝐴 ) |
10 |
9
|
albii |
⊢ ( ∀ 𝑦 [ 𝑦 / 𝑧 ] Ⅎ 𝑥 𝑧 ∈ 𝐴 ↔ ∀ 𝑦 Ⅎ 𝑥 𝑦 ∈ 𝐴 ) |
11 |
5 10
|
bitri |
⊢ ( ∀ 𝑧 Ⅎ 𝑥 𝑧 ∈ 𝐴 ↔ ∀ 𝑦 Ⅎ 𝑥 𝑦 ∈ 𝐴 ) |
12 |
2 11
|
bitri |
⊢ ( Ⅎ 𝑥 𝐴 ↔ ∀ 𝑦 Ⅎ 𝑥 𝑦 ∈ 𝐴 ) |