let F be Field; :: thesis: for E being FieldExtension of F
for K being b1 -extending FieldExtension of F
for T1 being finite F -algebraic Subset of E
for T2 being Subset of K st T1 = T2 holds
FAdj (F,T1) = FAdj (F,T2)

let E be FieldExtension of F; :: thesis: for K being E -extending FieldExtension of F
for T1 being finite F -algebraic Subset of E
for T2 being Subset of K st T1 = T2 holds
FAdj (F,T1) = FAdj (F,T2)

let K be E -extending FieldExtension of F; :: thesis: for T1 being finite F -algebraic Subset of E
for T2 being Subset of K st T1 = T2 holds
FAdj (F,T1) = FAdj (F,T2)

let T1 be finite F -algebraic Subset of E; :: thesis: for T2 being Subset of K st T1 = T2 holds
FAdj (F,T1) = FAdj (F,T2)

let T2 be Subset of K; :: thesis: ( T1 = T2 implies FAdj (F,T1) = FAdj (F,T2) )
assume AS: T1 = T2 ; :: thesis: FAdj (F,T1) = FAdj (F,T2)
defpred S1[ Nat] means for T1 being finite F -algebraic Subset of E
for T2 being Subset of K st card T1 = $1 & T1 = T2 holds
FAdj (F,T1) = FAdj (F,T2);
A: S1[ 0 ]
proof
now :: thesis: for T1 being finite F -algebraic Subset of E
for T2 being Subset of K st card T1 = 0 & T1 = T2 holds
FAdj (F,T1) = FAdj (F,T2)
let T1 be finite F -algebraic Subset of E; :: thesis: for T2 being Subset of K st card T1 = 0 & T1 = T2 holds
FAdj (F,T1) = FAdj (F,T2)

let T2 be Subset of K; :: thesis: ( card T1 = 0 & T1 = T2 implies FAdj (F,T1) = FAdj (F,T2) )
assume ( card T1 = 0 & T1 = T2 ) ; :: thesis: FAdj (F,T1) = FAdj (F,T2)
then ( T1 = {} & T2 = {} ) ;
then A1: ( T1 is Subset of F & T2 is Subset of F ) by XBOOLE_1:2;
then doubleLoopStr(# the carrier of (FAdj (F,T1)), the addF of (FAdj (F,T1)), the multF of (FAdj (F,T1)), the OneF of (FAdj (F,T1)), the ZeroF of (FAdj (F,T1)) #) = doubleLoopStr(# the carrier of F, the addF of F, the multF of F, the OneF of F, the ZeroF of F #) by FIELD_7:def 1, FIELD_7:3
.= doubleLoopStr(# the carrier of (FAdj (F,T2)), the addF of (FAdj (F,T2)), the multF of (FAdj (F,T2)), the OneF of (FAdj (F,T2)), the ZeroF of (FAdj (F,T2)) #) by A1, FIELD_7:def 1, FIELD_7:3 ;
hence FAdj (F,T1) = FAdj (F,T2) ; :: thesis: verum
end;
hence S1[ 0 ] ; :: thesis: verum
end;
B: now :: thesis: for k being Nat st S1[k] holds
S1[k + 1]
let k be Nat; :: thesis: ( S1[k] implies S1[k + 1] )
assume B0: S1[k] ; :: thesis: S1[k + 1]
B1: E is Subfield of K by FIELD_4:7;
then B2: the carrier of E c= the carrier of K by EC_PF_1:def 1;
now :: thesis: for T1 being finite F -algebraic Subset of E
for T2 being Subset of K st card T1 = k + 1 & T1 = T2 holds
FAdj (F,T1) = FAdj (F,T2)
let T1 be finite F -algebraic Subset of E; :: thesis: for T2 being Subset of K st card T1 = k + 1 & T1 = T2 holds
FAdj (F,T1) = FAdj (F,T2)

let T2 be Subset of K; :: thesis: ( card T1 = k + 1 & T1 = T2 implies FAdj (F,T1) = FAdj (F,T2) )
assume C0: ( card T1 = k + 1 & T1 = T2 ) ; :: thesis: FAdj (F,T1) = FAdj (F,T2)
then reconsider U1 = T1 as non empty finite Subset of E ;
set a = the Element of U1;
reconsider V1 = T1 \ { the Element of U1} as finite F -algebraic Subset of E ;
reconsider V2 = T2 \ { the Element of U1} as Subset of K ;
now :: thesis: for o being object st o in { the Element of U1} holds
o in T1
let o be object ; :: thesis: ( o in { the Element of U1} implies o in T1 )
assume o in { the Element of U1} ; :: thesis: o in T1
then o = the Element of U1 by TARSKI:def 1;
hence o in T1 ; :: thesis: verum
end;
then { the Element of U1} c= T1 ;
then C1: T1 = V1 \/ { the Element of U1} by XBOOLE_1:45;
the Element of U1 in { the Element of U1} by TARSKI:def 1;
then not the Element of U1 in V1 by XBOOLE_0:def 5;
then C2: card T1 = (card V1) + 1 by C1, CARD_2:41;
now :: thesis: for o being object st o in { the Element of U1} holds
o in T2
let o be object ; :: thesis: ( o in { the Element of U1} implies o in T2 )
assume o in { the Element of U1} ; :: thesis: o in T2
then o = the Element of U1 by TARSKI:def 1;
hence o in T2 by C0; :: thesis: verum
end;
then { the Element of U1} c= T2 ;
then C3: T2 = V2 \/ { the Element of U1} by XBOOLE_1:45;
C4: FAdj (F,V1) = FAdj (F,V2) by B0, C0, C2;
reconsider b = the Element of U1 as Element of K by B2;
consider p being non zero Polynomial of F such that
B: Ext_eval (p, the Element of U1) = 0. E by FIELD_6:43;
reconsider p = p as non zero Element of the carrier of (Polynom-Ring F) by POLYNOM3:def 10;
Ext_eval (p,b) = 0. E by B, FIELD_6:11
.= 0. K by B1, EC_PF_1:def 1 ;
then reconsider b = b as F -algebraic Element of K by FIELD_6:43;
reconsider E1 = E as F -extending FieldExtension of F by FIELD_4:7;
reconsider E2 = K as F -extending FieldExtension of F by FIELD_4:7;
consider p being non zero Polynomial of F such that
B: Ext_eval (p, the Element of U1) = 0. E by FIELD_6:43;
reconsider p = p as non zero Element of the carrier of (Polynom-Ring F) by POLYNOM3:def 10;
the carrier of (Polynom-Ring F) c= the carrier of (Polynom-Ring (FAdj (F,V1))) by FIELD_4:10;
then reconsider q = p as Element of the carrier of (Polynom-Ring (FAdj (F,V1))) ;
C: Polynom-Ring F is Subring of Polynom-Ring (FAdj (F,V1)) by FIELD_4:def 1;
now :: thesis: not q is zero
assume q is zero ; :: thesis: contradiction
then q = 0_. (FAdj (F,V1)) by UPROOTS:def 5
.= 0. (Polynom-Ring (FAdj (F,V1))) by POLYNOM3:def 10
.= 0. (Polynom-Ring F) by C, C0SP1:def 3
.= 0_. F by POLYNOM3:def 10 ;
hence contradiction ; :: thesis: verum
end;
then reconsider q = q as non zero Element of the carrier of (Polynom-Ring (FAdj (F,V1))) ;
Ext_eval (q, the Element of U1) = 0. E1 by B, FIELD_7:15;
then reconsider a1 = the Element of U1 as FAdj (F,V1) -algebraic Element of E1 by FIELD_6:43;
consider p being non zero Polynomial of F such that
B: Ext_eval (p,b) = 0. K by FIELD_6:43;
reconsider p = p as non zero Element of the carrier of (Polynom-Ring F) by POLYNOM3:def 10;
the carrier of (Polynom-Ring F) c= the carrier of (Polynom-Ring (FAdj (F,V2))) by FIELD_4:10;
then reconsider q = p as Element of the carrier of (Polynom-Ring (FAdj (F,V2))) ;
C: Polynom-Ring F is Subring of Polynom-Ring (FAdj (F,V2)) by FIELD_4:def 1;
now :: thesis: not q is zero
assume q is zero ; :: thesis: contradiction
then q = 0_. (FAdj (F,V2)) by UPROOTS:def 5
.= 0. (Polynom-Ring (FAdj (F,V2))) by POLYNOM3:def 10
.= 0. (Polynom-Ring F) by C, C0SP1:def 3
.= 0_. F by POLYNOM3:def 10 ;
hence contradiction ; :: thesis: verum
end;
then reconsider q = q as non zero Element of the carrier of (Polynom-Ring (FAdj (F,V2))) ;
Ext_eval (q,b) = 0. E2 by B, FIELD_7:15;
then reconsider b1 = b as FAdj (F,V2) -algebraic Element of E2 by FIELD_6:43;
thus FAdj (F,T1) = FAdj ((FAdj (F,V1)),{a1}) by C1, FIELD_7:34
.= FAdj ((FAdj (F,V2)),{b1}) by C4, FIELD_10:9
.= FAdj (F,T2) by C3, FIELD_7:34 ; :: thesis: verum
end;
hence S1[k + 1] ; :: thesis: verum
end;
I: for k being Nat holds S1[k] from NAT_1:sch 2(A, B);
consider n being Nat such that
H: card T1 = n ;
thus FAdj (F,T1) = FAdj (F,T2) by H, AS, I; :: thesis: verum