Step |
Hyp |
Ref |
Expression |
1 |
|
opabssxp |
⊢ { 〈 𝑒 , 𝑓 〉 ∣ ( ( 𝑒 ∈ Field ∧ 𝑓 ∈ Field ) ∧ ( 𝑓 = ( 𝑒 ↾s ( Base ‘ 𝑓 ) ) ∧ ( Base ‘ 𝑓 ) ∈ ( SubRing ‘ 𝑒 ) ) ) } ⊆ ( Field × Field ) |
2 |
|
df-br |
⊢ ( 𝐸 /FldExt 𝐹 ↔ 〈 𝐸 , 𝐹 〉 ∈ /FldExt ) |
3 |
2
|
biimpi |
⊢ ( 𝐸 /FldExt 𝐹 → 〈 𝐸 , 𝐹 〉 ∈ /FldExt ) |
4 |
|
df-fldext |
⊢ /FldExt = { 〈 𝑒 , 𝑓 〉 ∣ ( ( 𝑒 ∈ Field ∧ 𝑓 ∈ Field ) ∧ ( 𝑓 = ( 𝑒 ↾s ( Base ‘ 𝑓 ) ) ∧ ( Base ‘ 𝑓 ) ∈ ( SubRing ‘ 𝑒 ) ) ) } |
5 |
3 4
|
eleqtrdi |
⊢ ( 𝐸 /FldExt 𝐹 → 〈 𝐸 , 𝐹 〉 ∈ { 〈 𝑒 , 𝑓 〉 ∣ ( ( 𝑒 ∈ Field ∧ 𝑓 ∈ Field ) ∧ ( 𝑓 = ( 𝑒 ↾s ( Base ‘ 𝑓 ) ) ∧ ( Base ‘ 𝑓 ) ∈ ( SubRing ‘ 𝑒 ) ) ) } ) |
6 |
1 5
|
sselid |
⊢ ( 𝐸 /FldExt 𝐹 → 〈 𝐸 , 𝐹 〉 ∈ ( Field × Field ) ) |
7 |
|
opelxp1 |
⊢ ( 〈 𝐸 , 𝐹 〉 ∈ ( Field × Field ) → 𝐸 ∈ Field ) |
8 |
6 7
|
syl |
⊢ ( 𝐸 /FldExt 𝐹 → 𝐸 ∈ Field ) |