:: BROUWER semantic presentation

set c1 = TOP-REAL 2;

E1: [#] (TOP-REAL 2) = the carrier of (TOP-REAL 2)
by PRE_TOPC:12;

definition
let c2, c3 be non empty TopSpace;
func DiffElems c1,c2 -> Subset of [:a1,a2:] equals :: BROUWER:def 1
{ [b1,b2] where B is Point of a1, B is Point of a2 : b1 <> b2 } ;
coherence
{ [b1,b2] where B is Point of c2, B is Point of c3 : b1 <> b2 } is Subset of [:c2,c3:]
proof
set c4 = { [b1,b2] where B is Point of c2, B is Point of c3 : b1 <> b2 } ;
{ [b1,b2] where B is Point of c2, B is Point of c3 : b1 <> b2 } c= the carrier of [:c2,c3:]
proof
let c5 be set ; :: according to TARSKI:def 3
assume c5 in { [b1,b2] where B is Point of c2, B is Point of c3 : b1 <> b2 } ;
then ex b1 being Point of c2ex b2 being Point of c3 st
( c5 = [b1,b2] & b1 <> b2 ) ;
hence c5 in the carrier of [:c2,c3:] ;
end;
hence { [b1,b2] where B is Point of c2, B is Point of c3 : b1 <> b2 } is Subset of [:c2,c3:] ;
end;
end;

:: deftheorem defines DiffElems BROUWER:def 1 :
for b1, b2 being non empty TopSpace holds DiffElems b1,b2 = { [b3,b4] where B is Point of b1, B is Point of b2 : b3 <> b4 } ;

theorem :: BROUWER:1
for b1, b2 being non empty TopSpace
for b3 being set holds
( b3 in DiffElems b1,b2 iff ex b4 being Point of b1ex b5 being Point of b2 st
( b3 = [b4,b5] & b4 <> b5 ) ) ;

registration
let c2 be non empty non trivial TopSpace;
let c3 be non empty TopSpace;
cluster DiffElems a1,a2 -> non empty ;
coherence
not DiffElems c2,c3 is empty
proof
consider c4, c5 being Element of c2 such that
E2: c4 <> c5 by YELLOW_8:def 1;
consider c6 being Element of c3;
per cases not ( not c4 = c6 & not c4 <> c6 ) ;
suppose c4 = c6 ;
then [c5,c6] in DiffElems c2,c3 by E2;
hence not DiffElems c2,c3 is empty ;
end;
suppose c4 <> c6 ;
then [c4,c6] in DiffElems c2,c3 ;
hence not DiffElems c2,c3 is empty ;
end;
end;
end;
end;

registration
let c2 be non empty TopSpace;
let c3 be non empty non trivial TopSpace;
cluster DiffElems a1,a2 -> non empty ;
coherence
not DiffElems c2,c3 is empty
proof
consider c4 being Element of c2;
consider c5, c6 being Element of c3 such that
E2: c5 <> c6 by YELLOW_8:def 1;
per cases not ( not c4 = c5 & not c4 <> c5 ) ;
suppose c4 = c5 ;
then [c4,c6] in DiffElems c2,c3 by E2;
hence not DiffElems c2,c3 is empty ;
end;
suppose c4 <> c5 ;
then [c4,c5] in DiffElems c2,c3 ;
hence not DiffElems c2,c3 is empty ;
end;
end;
end;
end;

theorem E2: :: BROUWER:2
for b1 being Nat
for b2 being Point of (TOP-REAL b1) holds cl_Ball b2,0 = {b2}
proof
let c2 be Nat;
let c3 be Point of (TOP-REAL c2);
thus cl_Ball c3,0 c= {c3} :: according to XBOOLE_0:def 10
proof
let c4 be set ; :: according to TARSKI:def 3
assume E3: c4 in cl_Ball c3,0 ;
then reconsider c5 = c4 as Point of (TOP-REAL c2) ;
|.(c5 - c3).| <= 0 by E3, TOPREAL9:8;
then |.(c5 - c3).| = 0 by TOPRNS_1:26;
then c5 = c3 by TOPRNS_1:29;
hence c4 in {c3} by TARSKI:def 1;
end;
let c4 be set ; :: according to TARSKI:def 3
assume c4 in {c3} ;
then E3: c4 = c3 by TARSKI:def 1;
|.(c3 - c3).| = 0 by TOPRNS_1:29;
hence c4 in cl_Ball c3,0 by E3, TOPREAL9:8;
end;

definition
let c2 be Nat;
let c3 be Point of (TOP-REAL c2);
let c4 be real number ;
func Tdisk c2,c3 -> SubSpace of TOP-REAL a1 equals :: BROUWER:def 2
(TOP-REAL a1) | (cl_Ball a2,a3);
coherence
(TOP-REAL c2) | (cl_Ball c3,c4) is SubSpace of TOP-REAL c2
;
end;

:: deftheorem defines Tdisk BROUWER:def 2 :
for b1 being Nat
for b2 being Point of (TOP-REAL b1)
for b3 being real number holds Tdisk b2,b3 = (TOP-REAL b1) | (cl_Ball b2,b3);

registration
let c2 be Nat;
let c3 be Point of (TOP-REAL c2);
let c4 be real non negative number ;
cluster Tdisk a2,a3 -> non empty ;
coherence
not Tdisk c3,c4 is empty
;
end;

theorem E3: :: BROUWER:3
for b1 being Nat
for b2 being real number
for b3 being Point of (TOP-REAL b1) holds the carrier of (Tdisk b3,b2) = cl_Ball b3,b2
proof
let c2 be Nat;
let c3 be real number ;
let c4 be Point of (TOP-REAL c2);
[#] (Tdisk c4,c3) = cl_Ball c4,c3 by PRE_TOPC:def 10;
hence the carrier of (Tdisk c4,c3) = cl_Ball c4,c3 by PRE_TOPC:12;
end;

registration
let c2 be Nat;
let c3 be Point of (TOP-REAL c2);
let c4 be real number ;
cluster Tdisk a2,a3 -> convex ;
coherence
Tdisk c3,c4 is convex
proof
the carrier of (Tdisk c3,c4) = cl_Ball c3,c4 by E3;
hence [#] (Tdisk c3,c4) is convex Subset of (TOP-REAL c2) by PRE_TOPC:12; :: according to TOPALG_2:def 1
end;
end;

theorem E4: :: BROUWER:4
for b1 being Nat
for b2 being real non negative number
for b3, b4, b5 being Point of (TOP-REAL b1) holds
not ( b3 <> b4 & b3 is Point of (Tdisk b5,b2) & not b3 is Point of (Tcircle b5,b2) & ( for b6 being Point of (Tcircle b5,b2) holds
not {b6} = (halfline b3,b4) /\ (Sphere b5,b2) ) )
proof
let c2 be Nat;
let c3 be real non negative number ;
let c4, c5, c6 be Point of (TOP-REAL c2);
assume that
E5: c4 <> c5 and
E6: c4 is Point of (Tdisk c6,c3) and
E7: not c4 is Point of (Tcircle c6,c3) ;
E8: the carrier of (Tcircle c6,c3) = Sphere c6,c3 by TOPREALB:9;
E9: the carrier of (Tdisk c6,c3) = cl_Ball c6,c3 by E3;
E10: |.(c4 - c6).| <> c3 by E7, E8, TOPREAL9:9;
reconsider c7 = c4, c8 = c5, c9 = c6 as Element of REAL c2 by EUCLID:25;
set c10 = ((- (2 * |((c5 - c4),(c4 - c6))|)) + (sqrt (delta (Sum (sqr (c8 - c7))),(2 * |((c5 - c4),(c4 - c6))|),((Sum (sqr (c7 - c9))) - (c3 ^2 ))))) / (2 * (Sum (sqr (c8 - c7))));
|.(c4 - c6).| <= c3 by E6, E9, TOPREAL9:8;
then |.(c4 - c6).| < c3 by E10, REAL_1:def 5;
then c4 in Ball c6,c3 by TOPREAL9:7;
then consider c11 being Point of (TOP-REAL c2) such that
E11: {c11} = (halfline c4,c5) /\ (Sphere c6,c3) and
c11 = ((1 - (((- (2 * |((c5 - c4),(c4 - c6))|)) + (sqrt (delta (Sum (sqr (c8 - c7))),(2 * |((c5 - c4),(c4 - c6))|),((Sum (sqr (c7 - c9))) - (c3 ^2 ))))) / (2 * (Sum (sqr (c8 - c7)))))) * c4) + ((((- (2 * |((c5 - c4),(c4 - c6))|)) + (sqrt (delta (Sum (sqr (c8 - c7))),(2 * |((c5 - c4),(c4 - c6))|),((Sum (sqr (c7 - c9))) - (c3 ^2 ))))) / (2 * (Sum (sqr (c8 - c7))))) * c5) by E5, TOPREAL9:37;
c11 in {c11} by TARSKI:def 1;
then c11 in Sphere c6,c3 by E11, XBOOLE_0:def 3;
hence ex b1 being Point of (Tcircle c6,c3) st {b1} = (halfline c4,c5) /\ (Sphere c6,c3) by E8, E11;
end;

theorem E5: :: BROUWER:5
for b1 being Nat
for b2 being real non negative number
for b3, b4, b5 being Point of (TOP-REAL b1) holds
not ( b3 <> b4 & b3 in the carrier of (Tcircle b5,b2) & b4 is Point of (Tdisk b5,b2) & ( for b6 being Point of (Tcircle b5,b2) holds
not ( b6 <> b3 & {b3,b6} = (halfline b3,b4) /\ (Sphere b5,b2) ) ) )
proof
let c2 be Nat;
let c3 be real non negative number ;
let c4, c5, c6 be Point of (TOP-REAL c2);
assume that
E6: c4 <> c5 and
E7: c4 in the carrier of (Tcircle c6,c3) and
E8: c5 is Point of (Tdisk c6,c3) ;
E9: the carrier of (Tcircle c6,c3) = Sphere c6,c3 by TOPREALB:9;
reconsider c7 = ((1 / 2) * c4) + ((1 / 2) * c5), c8 = c5, c9 = c6 as Element of REAL c2 by EUCLID:25;
set c10 = ((- (2 * |((c5 - (((1 / 2) * c4) + ((1 / 2) * c5))),((((1 / 2) * c4) + ((1 / 2) * c5)) - c6))|)) + (sqrt (delta (Sum (sqr (c8 - c7))),(2 * |((c5 - (((1 / 2) * c4) + ((1 / 2) * c5))),((((1 / 2) * c4) + ((1 / 2) * c5)) - c6))|),((Sum (sqr (c7 - c9))) - (c3 ^2 ))))) / (2 * (Sum (sqr (c8 - c7))));
the carrier of (Tdisk c6,c3) = cl_Ball c6,c3 by E3;
then consider c11 being Point of (TOP-REAL c2) such that
E10: c11 <> c4 and
E11: {c4,c11} = (halfline c4,c5) /\ (Sphere c6,c3) and
( ( c5 in Sphere c6,c3 implies c11 = c5 ) & ( ( ((- (2 * |((c5 - (((1 / 2) * c4) + ((1 / 2) * c5))),((((1 / 2) * c4) + ((1 / 2) * c5)) - c6))|)) + (sqrt (delta (Sum (sqr (c8 - c7))),(2 * |((c5 - (((1 / 2) * c4) + ((1 / 2) * c5))),((((1 / 2) * c4) + ((1 / 2) * c5)) - c6))|),((Sum (sqr (c7 - c9))) - (c3 ^2 ))))) / (2 * (Sum (sqr (c8 - c7)))) = ((- (2 * |((c5 - (((1 / 2) * c4) + ((1 / 2) * c5))),((((1 / 2) * c4) + ((1 / 2) * c5)) - c6))|)) + (sqrt (delta (Sum (sqr (c8 - c7))),(2 * |((c5 - (((1 / 2) * c4) + ((1 / 2) * c5))),((((1 / 2) * c4) + ((1 / 2) * c5)) - c6))|),((Sum (sqr (c7 - c9))) - (c3 ^2 ))))) / (2 * (Sum (sqr (c8 - c7)))) ) implies ( c5 in Sphere c6,c3 or c11 = ((1 - (((- (2 * |((c5 - (((1 / 2) * c4) + ((1 / 2) * c5))),((((1 / 2) * c4) + ((1 / 2) * c5)) - c6))|)) + (sqrt (delta (Sum (sqr (c8 - c7))),(2 * |((c5 - (((1 / 2) * c4) + ((1 / 2) * c5))),((((1 / 2) * c4) + ((1 / 2) * c5)) - c6))|),((Sum (sqr (c7 - c9))) - (c3 ^2 ))))) / (2 * (Sum (sqr (c8 - c7)))))) * (((1 / 2) * c4) + ((1 / 2) * c5))) + ((((- (2 * |((c5 - (((1 / 2) * c4) + ((1 / 2) * c5))),((((1 / 2) * c4) + ((1 / 2) * c5)) - c6))|)) + (sqrt (delta (Sum (sqr (c8 - c7))),(2 * |((c5 - (((1 / 2) * c4) + ((1 / 2) * c5))),((((1 / 2) * c4) + ((1 / 2) * c5)) - c6))|),((Sum (sqr (c7 - c9))) - (c3 ^2 ))))) / (2 * (Sum (sqr (c8 - c7))))) * c5) ) ) ) by E8, E6, E9, E7, TOPREAL9:38;
( c11 in {c4,c11} & c4 in {c4,c11} ) by TARSKI:def 2;
then ( c11 in Sphere c6,c3 & c4 in Sphere c6,c3 ) by E11, XBOOLE_0:def 3;
hence ex b1 being Point of (Tcircle c6,c3) st
( b1 <> c4 & {c4,b1} = (halfline c4,c5) /\ (Sphere c6,c3) ) by E9, E10, E11;
end;

definition
let c2 be non empty Nat;
let c3 be Point of (TOP-REAL c2);
let c4, c5 be Point of (TOP-REAL c2);
let c6 be real non negative number ;
assume that
E6: c4 is Point of (Tdisk c3,c6) and
E7: c5 is Point of (Tdisk c3,c6) and
E8: c4 <> c5 ;
func HC c3,c4,c2,c5 -> Point of (TOP-REAL a1) means :E6: :: BROUWER:def 3
( a6 in (halfline a3,a4) /\ (Sphere a2,a5) & a6 <> a3 );
existence
ex b1 being Point of (TOP-REAL c2) st
( b1 in (halfline c4,c5) /\ (Sphere c3,c6) & b1 <> c4 )
proof
per cases not ( not c4 is Point of (Tcircle c3,c6) & c4 is Point of (Tcircle c3,c6) ) ;
suppose E9: c4 is Point of (Tcircle c3,c6) ;
consider c7 being Point of (Tcircle c3,c6) such that
E10: ( c7 <> c4 & {c4,c7} = (halfline c4,c5) /\ (Sphere c3,c6) ) by E7, E8, E9, E5;
reconsider c8 = c7 as Point of (TOP-REAL c2) by TOPMETR:2;
take c8 ;
thus ( c8 in (halfline c4,c5) /\ (Sphere c3,c6) & c8 <> c4 ) by E10, TARSKI:def 2;
end;
suppose E9: not c4 is Point of (Tcircle c3,c6) ;
consider c7 being Point of (Tcircle c3,c6) such that
E10: {c7} = (halfline c4,c5) /\ (Sphere c3,c6) by E9, E8, E6, E4;
reconsider c8 = c7 as Point of (TOP-REAL c2) by TOPMETR:2;
take c8 ;
thus ( c8 in (halfline c4,c5) /\ (Sphere c3,c6) & c8 <> c4 ) by E10, E9, TARSKI:def 1;
end;
end;
end;
uniqueness
for b1, b2 being Point of (TOP-REAL c2) holds
( ( b1 in (halfline c4,c5) /\ (Sphere c3,c6) & b2 in (halfline c4,c5) /\ (Sphere c3,c6) ) implies ( not b1 <> c4 or not b2 <> c4 or b1 = b2 ) )
proof
let c7, c8 be Point of (TOP-REAL c2);
assume that
E9: ( c7 in (halfline c4,c5) /\ (Sphere c3,c6) & c7 <> c4 ) and
E10: ( c8 in (halfline c4,c5) /\ (Sphere c3,c6) & c8 <> c4 ) ;
per cases not ( not c4 is Point of (Tcircle c3,c6) & c4 is Point of (Tcircle c3,c6) ) ;
suppose E11: c4 is Point of (Tcircle c3,c6) ;
consider c9 being Point of (Tcircle c3,c6) such that
c9 <> c4 and
E12: {c4,c9} = (halfline c4,c5) /\ (Sphere c3,c6) by E7, E8, E11, E5;
per cases not ( not ( c7 = c9 & c8 = c9 ) & not ( c7 = c9 & c8 = c4 ) & not ( c7 = c4 & c8 = c9 ) & not ( c7 = c4 & c8 = c4 ) ) by E9, E10, E12, TARSKI:def 2;
suppose ( c7 = c9 & c8 = c9 ) ;
hence c7 = c8 ;
end;
suppose ( c7 = c9 & c8 = c4 ) ;
hence c7 = c8 by E10;
end;
suppose ( c7 = c4 & c8 = c9 ) ;
hence c7 = c8 by E9;
end;
suppose ( c7 = c4 & c8 = c4 ) ;
hence c7 = c8 ;
end;
end;
end;
suppose E11: not c4 is Point of (Tcircle c3,c6) ;
consider c9 being Point of (Tcircle c3,c6) such that
E12: {c9} = (halfline c4,c5) /\ (Sphere c3,c6) by E11, E6, E8, E4;
c7 = c9 by E9, E12, TARSKI:def 1;
hence c7 = c8 by E10, E12, TARSKI:def 1;
end;
end;
end;
end;

:: deftheorem E6 defines HC BROUWER:def 3 :
for b1 being non empty Nat
for b2, b3, b4 being Point of (TOP-REAL b1)
for b5 being real non negative number holds
( ( b3 is Point of (Tdisk b2,b5) & b4 is Point of (Tdisk b2,b5) ) implies ( not b3 <> b4 or ( for b6 being Point of (TOP-REAL b1) holds
( b6 = HC b3,b4,b2,b5 iff ( b6 in (halfline b3,b4) /\ (Sphere b2,b5) & b6 <> b3 ) ) ) ) );

theorem E7: :: BROUWER:6
for b1 being real non negative number
for b2 being non empty Nat
for b3, b4, b5 being Point of (TOP-REAL b2) holds
( ( b3 is Point of (Tdisk b4,b1) & b5 is Point of (Tdisk b4,b1) ) implies ( not b3 <> b5 or HC b3,b5,b4,b1 is Point of (Tcircle b4,b1) ) )
proof
let c2 be real non negative number ;
let c3 be non empty Nat;
let c4, c5, c6 be Point of (TOP-REAL c3);
assume E8: ( c4 is Point of (Tdisk c5,c2) & c6 is Point of (Tdisk c5,c2) & c4 <> c6 ) ;
E9: the carrier of (Tcircle c5,c2) = Sphere c5,c2 by TOPREALB:9;
HC c4,c6,c5,c2 in (halfline c4,c6) /\ (Sphere c5,c2) by E8, E6;
hence HC c4,c6,c5,c2 is Point of (Tcircle c5,c2) by E9, XBOOLE_0:def 3;
end;

theorem :: BROUWER:7
for b1 being real number
for b2 being real non negative number
for b3 being non empty Nat
for b4, b5, b6 being Point of (TOP-REAL b3)
for b7, b8, b9 being Element of REAL b3 holds
( ( b7 = b4 & b8 = b5 & b9 = b6 & b4 is Point of (Tdisk b6,b2) & b5 is Point of (Tdisk b6,b2) & b1 = ((- |((b5 - b4),(b4 - b6))|) + (sqrt ((|((b5 - b4),(b4 - b6))| ^2 ) - ((Sum (sqr (b8 - b7))) * ((Sum (sqr (b7 - b9))) - (b2 ^2 )))))) / (Sum (sqr (b8 - b7))) ) implies ( not b4 <> b5 or HC b4,b5,b6,b2 = ((1 - b1) * b4) + (b1 * b5) ) )
proof
let c2 be real number ;
let c3 be real non negative number ;
let c4 be non empty Nat;
let c5, c6, c7 be Point of (TOP-REAL c4);
let c8, c9, c10 be Element of REAL c4;
assume that
E8: ( c8 = c5 & c9 = c6 & c10 = c7 ) and
E9: c5 is Point of (Tdisk c7,c3) and
E10: c6 is Point of (Tdisk c7,c3) and
E11: c5 <> c6 ;
set c11 = HC c5,c6,c7,c3;
set c12 = |((c6 - c5),(c5 - c7))|;
set c13 = Sum (sqr (c9 - c8));
set c14 = 2 * |((c6 - c5),(c5 - c7))|;
set c15 = (Sum (sqr (c8 - c10))) - (c3 ^2 );
set c16 = ((- (2 * |((c6 - c5),(c5 - c7))|)) - (sqrt (delta (Sum (sqr (c9 - c8))),(2 * |((c6 - c5),(c5 - c7))|),((Sum (sqr (c8 - c10))) - (c3 ^2 ))))) / (2 * (Sum (sqr (c9 - c8))));
set c17 = ((- (2 * |((c6 - c5),(c5 - c7))|)) + (sqrt (delta (Sum (sqr (c9 - c8))),(2 * |((c6 - c5),(c5 - c7))|),((Sum (sqr (c8 - c10))) - (c3 ^2 ))))) / (2 * (Sum (sqr (c9 - c8))));
assume E12: c2 = ((- |((c6 - c5),(c5 - c7))|) + (sqrt ((|((c6 - c5),(c5 - c7))| ^2 ) - ((Sum (sqr (c9 - c8))) * ((Sum (sqr (c8 - c10))) - (c3 ^2 )))))) / (Sum (sqr (c9 - c8))) ;
E13: HC c5,c6,c7,c3 in (halfline c5,c6) /\ (Sphere c7,c3) by E9, E10, E11, E6;
then HC c5,c6,c7,c3 in halfline c5,c6 by XBOOLE_0:def 3;
then consider c18 being real number such that
E14: HC c5,c6,c7,c3 = ((1 - c18) * c5) + (c18 * c6) and
E15: 0 <= c18 by TOPREAL9:26;
E16: HC c5,c6,c7,c3 = ((1 * c5) - (c18 * c5)) + (c18 * c6) by E14, EUCLID:54
.= (c5 - (c18 * c5)) + (c18 * c6) by EUCLID:33
.= (c5 + (c18 * c6)) - (c18 * c5) by JORDAN2C:9
.= c5 + ((c18 * c6) - (c18 * c5)) by EUCLID:49
.= c5 + (c18 * (c6 - c5)) by EUCLID:53 ;
E17: |.(c9 - c8).| <> 0 by E8, E11, EUCLID:19;
E18: now
assume Sum (sqr (c9 - c8)) <= 0 ;
then Sum (sqr (c9 - c8)) = 0 by RVSUM_1:116;
hence not verum by E17, EUCLID:def 5, SQUARE_1:82;
end;
E19: delta (Sum (sqr (c9 - c8))),(2 * |((c6 - c5),(c5 - c7))|),((Sum (sqr (c8 - c10))) - (c3 ^2 )) = ((2 * |((c6 - c5),(c5 - c7))|) ^2 ) - ((4 * (Sum (sqr (c9 - c8)))) * ((Sum (sqr (c8 - c10))) - (c3 ^2 ))) by QUIN_1:def 1
.= ((2 ^2 ) * (|((c6 - c5),(c5 - c7))| ^2 )) - ((4 * (Sum (sqr (c9 - c8)))) * ((Sum (sqr (c8 - c10))) - (c3 ^2 )))
.= ((2 * 2) * (|((c6 - c5),(c5 - c7))| ^2 )) - ((4 * (Sum (sqr (c9 - c8)))) * ((Sum (sqr (c8 - c10))) - (c3 ^2 )))
.= 4 * ((|((c6 - c5),(c5 - c7))| ^2 ) - ((Sum (sqr (c9 - c8))) * ((Sum (sqr (c8 - c10))) - (c3 ^2 )))) ;
the carrier of (Tdisk c7,c3) = cl_Ball c7,c3 by E3;
then E20: |.(c5 - c7).| <= c3 by E9, TOPREAL9:8;
E21: |.(c8 - c10).| = sqrt (Sum (sqr (c8 - c10))) by EUCLID:def 5;
E22: |.(c8 - c10).| >= 0 by EUCLID:12;
c6 - c5 = c9 - c8 by E8, EUCLID:def 13;
then E23: |.(c6 - c5).| = |.(c9 - c8).| by TOPRNS_1:def 6;
E24: |.(c9 - c8).| = sqrt (Sum (sqr (c9 - c8))) by EUCLID:def 5;
Sum (sqr (c9 - c8)) >= 0 by RVSUM_1:116;
then E25: |.(c9 - c8).| ^2 = Sum (sqr (c9 - c8)) by E24, SQUARE_1:def 4;
Sum (sqr (c8 - c10)) >= 0 by RVSUM_1:116;
then E26: |.(c8 - c10).| ^2 = Sum (sqr (c8 - c10)) by E21, SQUARE_1:def 4;
c5 - c7 = c8 - c10 by E8, EUCLID:def 13;
then E27: |.(c5 - c7).| = |.(c8 - c10).| by TOPRNS_1:def 6;
then E28: (sqrt (Sum (sqr (c8 - c10)))) ^2 <= c3 ^2 by E20, E21, E22, SQUARE_1:77;
then E29: (Sum (sqr (c8 - c10))) - (c3 ^2 ) <= 0 by E21, E26, REAL_2:106;
E30: delta (Sum (sqr (c9 - c8))),(2 * |((c6 - c5),(c5 - c7))|),((Sum (sqr (c8 - c10))) - (c3 ^2 )) = ((2 * |((c6 - c5),(c5 - c7))|) ^2 ) - ((4 * (Sum (sqr (c9 - c8)))) * ((Sum (sqr (c8 - c10))) - (c3 ^2 ))) by QUIN_1:def 1;
4 * (Sum (sqr (c9 - c8))) > 0 by E18, XREAL_1:131;
then E31: (4 * (Sum (sqr (c9 - c8)))) * ((Sum (sqr (c8 - c10))) - (c3 ^2 )) <= 0 by E29, XREAL_1:133;
E32: ((2 * |((c6 - c5),(c5 - c7))|) ^2 ) - ((4 * (Sum (sqr (