Step |
Hyp |
Ref |
Expression |
1 |
|
df-ss |
⊢ ( 𝑌 ⊆ 𝐴 ↔ ( 𝑌 ∩ 𝐴 ) = 𝑌 ) |
2 |
|
sneq |
⊢ ( ( 𝑌 ∩ 𝐴 ) = 𝑌 → { ( 𝑌 ∩ 𝐴 ) } = { 𝑌 } ) |
3 |
1 2
|
sylbi |
⊢ ( 𝑌 ⊆ 𝐴 → { ( 𝑌 ∩ 𝐴 ) } = { 𝑌 } ) |
4 |
|
ssexg |
⊢ ( ( 𝑌 ⊆ 𝐴 ∧ 𝐴 ∈ 𝑉 ) → 𝑌 ∈ V ) |
5 |
4
|
ancoms |
⊢ ( ( 𝐴 ∈ 𝑉 ∧ 𝑌 ⊆ 𝐴 ) → 𝑌 ∈ V ) |
6 |
|
bj-restsn |
⊢ ( ( 𝑌 ∈ V ∧ 𝐴 ∈ 𝑉 ) → ( { 𝑌 } ↾t 𝐴 ) = { ( 𝑌 ∩ 𝐴 ) } ) |
7 |
6
|
ancoms |
⊢ ( ( 𝐴 ∈ 𝑉 ∧ 𝑌 ∈ V ) → ( { 𝑌 } ↾t 𝐴 ) = { ( 𝑌 ∩ 𝐴 ) } ) |
8 |
5 7
|
syldan |
⊢ ( ( 𝐴 ∈ 𝑉 ∧ 𝑌 ⊆ 𝐴 ) → ( { 𝑌 } ↾t 𝐴 ) = { ( 𝑌 ∩ 𝐴 ) } ) |
9 |
|
eqeq2 |
⊢ ( { ( 𝑌 ∩ 𝐴 ) } = { 𝑌 } → ( ( { 𝑌 } ↾t 𝐴 ) = { ( 𝑌 ∩ 𝐴 ) } ↔ ( { 𝑌 } ↾t 𝐴 ) = { 𝑌 } ) ) |
10 |
9
|
biimpa |
⊢ ( ( { ( 𝑌 ∩ 𝐴 ) } = { 𝑌 } ∧ ( { 𝑌 } ↾t 𝐴 ) = { ( 𝑌 ∩ 𝐴 ) } ) → ( { 𝑌 } ↾t 𝐴 ) = { 𝑌 } ) |
11 |
3 8 10
|
syl2an2 |
⊢ ( ( 𝐴 ∈ 𝑉 ∧ 𝑌 ⊆ 𝐴 ) → ( { 𝑌 } ↾t 𝐴 ) = { 𝑌 } ) |