Step |
Hyp |
Ref |
Expression |
1 |
|
eqimss |
⊢ ( 𝐴 = 𝐵 → 𝐴 ⊆ 𝐵 ) |
2 |
|
df-ss |
⊢ ( 𝐴 ⊆ 𝐵 ↔ ( 𝐴 ∩ 𝐵 ) = 𝐴 ) |
3 |
1 2
|
sylib |
⊢ ( 𝐴 = 𝐵 → ( 𝐴 ∩ 𝐵 ) = 𝐴 ) |
4 |
|
eleq1 |
⊢ ( ( 𝐴 ∩ 𝐵 ) = 𝐴 → ( ( 𝐴 ∩ 𝐵 ) ∈ 𝑉 ↔ 𝐴 ∈ 𝑉 ) ) |
5 |
4
|
biimpac |
⊢ ( ( ( 𝐴 ∩ 𝐵 ) ∈ 𝑉 ∧ ( 𝐴 ∩ 𝐵 ) = 𝐴 ) → 𝐴 ∈ 𝑉 ) |
6 |
3 5
|
sylan2 |
⊢ ( ( ( 𝐴 ∩ 𝐵 ) ∈ 𝑉 ∧ 𝐴 = 𝐵 ) → 𝐴 ∈ 𝑉 ) |
7 |
6
|
elexd |
⊢ ( ( ( 𝐴 ∩ 𝐵 ) ∈ 𝑉 ∧ 𝐴 = 𝐵 ) → 𝐴 ∈ V ) |
8 |
|
eqimss2 |
⊢ ( 𝐴 = 𝐵 → 𝐵 ⊆ 𝐴 ) |
9 |
|
sseqin2 |
⊢ ( 𝐵 ⊆ 𝐴 ↔ ( 𝐴 ∩ 𝐵 ) = 𝐵 ) |
10 |
8 9
|
sylib |
⊢ ( 𝐴 = 𝐵 → ( 𝐴 ∩ 𝐵 ) = 𝐵 ) |
11 |
|
eleq1 |
⊢ ( ( 𝐴 ∩ 𝐵 ) = 𝐵 → ( ( 𝐴 ∩ 𝐵 ) ∈ 𝑉 ↔ 𝐵 ∈ 𝑉 ) ) |
12 |
11
|
biimpac |
⊢ ( ( ( 𝐴 ∩ 𝐵 ) ∈ 𝑉 ∧ ( 𝐴 ∩ 𝐵 ) = 𝐵 ) → 𝐵 ∈ 𝑉 ) |
13 |
10 12
|
sylan2 |
⊢ ( ( ( 𝐴 ∩ 𝐵 ) ∈ 𝑉 ∧ 𝐴 = 𝐵 ) → 𝐵 ∈ 𝑉 ) |
14 |
13
|
elexd |
⊢ ( ( ( 𝐴 ∩ 𝐵 ) ∈ 𝑉 ∧ 𝐴 = 𝐵 ) → 𝐵 ∈ V ) |
15 |
7 14
|
jca |
⊢ ( ( ( 𝐴 ∩ 𝐵 ) ∈ 𝑉 ∧ 𝐴 = 𝐵 ) → ( 𝐴 ∈ V ∧ 𝐵 ∈ V ) ) |