Step |
Hyp |
Ref |
Expression |
1 |
|
fneqeql |
⊢ ( ( 𝐹 Fn 𝐴 ∧ 𝐺 Fn 𝐴 ) → ( 𝐹 = 𝐺 ↔ dom ( 𝐹 ∩ 𝐺 ) = 𝐴 ) ) |
2 |
|
inss1 |
⊢ ( 𝐹 ∩ 𝐺 ) ⊆ 𝐹 |
3 |
|
dmss |
⊢ ( ( 𝐹 ∩ 𝐺 ) ⊆ 𝐹 → dom ( 𝐹 ∩ 𝐺 ) ⊆ dom 𝐹 ) |
4 |
2 3
|
ax-mp |
⊢ dom ( 𝐹 ∩ 𝐺 ) ⊆ dom 𝐹 |
5 |
|
fndm |
⊢ ( 𝐹 Fn 𝐴 → dom 𝐹 = 𝐴 ) |
6 |
5
|
adantr |
⊢ ( ( 𝐹 Fn 𝐴 ∧ 𝐺 Fn 𝐴 ) → dom 𝐹 = 𝐴 ) |
7 |
4 6
|
sseqtrid |
⊢ ( ( 𝐹 Fn 𝐴 ∧ 𝐺 Fn 𝐴 ) → dom ( 𝐹 ∩ 𝐺 ) ⊆ 𝐴 ) |
8 |
7
|
biantrurd |
⊢ ( ( 𝐹 Fn 𝐴 ∧ 𝐺 Fn 𝐴 ) → ( 𝐴 ⊆ dom ( 𝐹 ∩ 𝐺 ) ↔ ( dom ( 𝐹 ∩ 𝐺 ) ⊆ 𝐴 ∧ 𝐴 ⊆ dom ( 𝐹 ∩ 𝐺 ) ) ) ) |
9 |
|
eqss |
⊢ ( dom ( 𝐹 ∩ 𝐺 ) = 𝐴 ↔ ( dom ( 𝐹 ∩ 𝐺 ) ⊆ 𝐴 ∧ 𝐴 ⊆ dom ( 𝐹 ∩ 𝐺 ) ) ) |
10 |
8 9
|
syl6rbbr |
⊢ ( ( 𝐹 Fn 𝐴 ∧ 𝐺 Fn 𝐴 ) → ( dom ( 𝐹 ∩ 𝐺 ) = 𝐴 ↔ 𝐴 ⊆ dom ( 𝐹 ∩ 𝐺 ) ) ) |
11 |
1 10
|
bitrd |
⊢ ( ( 𝐹 Fn 𝐴 ∧ 𝐺 Fn 𝐴 ) → ( 𝐹 = 𝐺 ↔ 𝐴 ⊆ dom ( 𝐹 ∩ 𝐺 ) ) ) |