set F = FAdj (F_Rat,{3-CRoot(2),zeta});
Roots (F_Complex,X^3-2) c= the carrier of (FAdj (F_Rat,{3-CRoot(2),zeta}))
proof
A1:
{3-CRoot(2),zeta} is
Subset of
(FAdj (F_Rat,{3-CRoot(2),zeta}))
by FIELD_6:35;
(
3-Root(2) in {3-CRoot(2),zeta} &
zeta in {3-CRoot(2),zeta} )
by TARSKI:def 2;
then reconsider a =
3-Root(2) ,
b =
zeta as
Element of
(FAdj (F_Rat,{3-CRoot(2),zeta})) by A1;
A3:
FAdj (
F_Rat,
{3-CRoot(2),zeta}) is
Subring of
F_Complex
by FIELD_4:def 1;
A5:
zeta * zeta = b * b
by A3, FIELD_6:16;
hence
Roots (
F_Complex,
X^3-2)
c= the
carrier of
(FAdj (F_Rat,{3-CRoot(2),zeta}))
;
verum
end;
then B:
X^3-2 splits_in FAdj (F_Rat,{3-CRoot(2),zeta})
by LLsplit, FIELD_8:27;
now for E being FieldExtension of F_Rat st X^3-2 splits_in E & E is Subfield of FAdj (F_Rat,{3-CRoot(2),zeta}) holds
E == FAdj (F_Rat,{3-CRoot(2),zeta})let E be
FieldExtension of
F_Rat ;
( X^3-2 splits_in E & E is Subfield of FAdj (F_Rat,{3-CRoot(2),zeta}) implies E == FAdj (F_Rat,{3-CRoot(2),zeta}) )assume C:
(
X^3-2 splits_in E &
E is
Subfield of
FAdj (
F_Rat,
{3-CRoot(2),zeta}) )
;
E == FAdj (F_Rat,{3-CRoot(2),zeta})then E:
E is
Subfield of
F_Complex
by EC_PF_1:5;
then F:
E is
Subring of
F_Complex
by FIELD_5:12;
D:
F_Rat is
Subfield of
E
by FIELD_4:7;
{3-CRoot(2),zeta} is
Subset of
E
proof
F_Complex is
E -extending
by E, FIELD_4:7;
then A1:
Roots (
F_Complex,
X^3-2)
c= the
carrier of
E
by LLsplit, C, FIELD_8:27;
(
3-Root(2) in Roots (
F_Complex,
X^3-2) &
3-CRoot(2) * zeta in Roots (
F_Complex,
X^3-2) )
by lemroots, ENUMSET1:def 1;
then reconsider a =
3-Root(2) ,
b =
3-CRoot(2) * zeta as
Element of
E by A1;
A3:
not
3-CRoot(2) is
zero
;
a " = 3-CRoot(2) "
by E, FIELD_6:18;
then A4:
(a ") * b =
(3-CRoot(2) ") * (3-CRoot(2) * zeta)
by F, FIELD_6:16
.=
((3-CRoot(2) ") * 3-CRoot(2)) * zeta
.=
(1. F_Complex) * zeta
by A3, VECTSP_2:9
;
then
{3-CRoot(2),zeta} c= the
carrier of
E
;
hence
{3-CRoot(2),zeta} is
Subset of
E
;
verum
end; then
FAdj (
F_Rat,
{3-CRoot(2),zeta}) is
Subfield of
E
by D, E, FIELD_6:37;
hence
E == FAdj (
F_Rat,
{3-CRoot(2),zeta})
by C, FIELD_7:def 2;
verum end;
hence
FAdj (F_Rat,{3-CRoot(2),zeta}) is SplittingField of X^3-2
by B, FIELD_8:def 1; verum