let P be Element of absolute ; ex Q being Element of absolute st P <> Q
P in conic (1,1,(- 1),0,0,0)
;
then
P in { P where P is Point of (ProjectiveSpace (TOP-REAL 3)) : for u being Element of (TOP-REAL 3) st not u is zero & P = Dir u holds
qfconic (1,1,(- 1),0,0,0,u) = 0 }
by PASCAL:def 2;
then consider Q being Point of (ProjectiveSpace (TOP-REAL 3)) such that
A1:
P = Q
and
A2:
for u being Element of (TOP-REAL 3) st not u is zero & Q = Dir u holds
qfconic (1,1,(- 1),0,0,0,u) = 0
;
consider u being Element of (TOP-REAL 3) such that
A3:
not u is zero
and
A4:
Dir u = P
by ANPROJ_1:26;
A5:
qfconic (1,1,(- 1),0,0,0,u) = 0
by A1, A2, A3, A4;
A6:
u . 3 <> 0
by A3, A4, Th67;
not |[(u . 1),(u . 2),(- (u . 3))]| is zero
then reconsider v = |[(u . 1),(u . 2),(- (u . 3))]| as non zero Element of (TOP-REAL 3) ;
reconsider R = Dir v as Element of (ProjectiveSpace (TOP-REAL 3)) by ANPROJ_1:26;
take
R
; ( R is Element of absolute & P <> R )
A7:
R <> P
for w being Element of (TOP-REAL 3) st not w is zero & R = Dir w holds
qfconic (1,1,(- 1),0,0,0,w) = 0
proof
let w be
Element of
(TOP-REAL 3);
( not w is zero & R = Dir w implies qfconic (1,1,(- 1),0,0,0,w) = 0 )
assume that A13:
not
w is
zero
and A14:
R = Dir w
;
qfconic (1,1,(- 1),0,0,0,w) = 0
are_Prop v,
w
by A13, A14, ANPROJ_1:22;
then consider b being
Real such that
b <> 0
and A15:
w = b * v
by ANPROJ_1:1;
A16:
w . 1 =
b * (v . 1)
by A15, RVSUM_1:44
.=
b * (v `1)
by EUCLID_5:def 1
.=
b * (u . 1)
by EUCLID_5:2
;
A17:
w . 2 =
b * (v . 2)
by A15, RVSUM_1:44
.=
b * (v `2)
by EUCLID_5:def 2
.=
b * (u . 2)
by EUCLID_5:2
;
A18:
w . 3 =
b * (v . 3)
by A15, RVSUM_1:44
.=
b * (v `3)
by EUCLID_5:def 3
.=
b * (- (u . 3))
by EUCLID_5:2
;
qfconic (1,1,
(- 1),
0,
0,
0,
w) =
((((((1 * (w . 1)) * (w . 1)) + ((1 * (w . 2)) * (w . 2))) + (((- 1) * (w . 3)) * (w . 3))) + ((0 * (w . 1)) * (w . 2))) + ((0 * (w . 1)) * (w . 3))) + ((0 * (w . 2)) * (w . 3))
by PASCAL:def 1
.=
(b * b) * (((((((1 * (u . 1)) * (u . 1)) + ((1 * (u . 2)) * (u . 2))) + (((- 1) * (u . 3)) * (u . 3))) + ((0 * (u . 1)) * (u . 2))) + ((0 * (u . 1)) * (u . 3))) + ((0 * (u . 2)) * (u . 3)))
by A16, A17, A18
.=
(b * b) * (qfconic (1,1,(- 1),0,0,0,u))
by PASCAL:def 1
.=
0
by A5
;
hence
qfconic (1,1,
(- 1),
0,
0,
0,
w)
= 0
;
verum
end;
then
R in { P where P is Point of (ProjectiveSpace (TOP-REAL 3)) : for u being Element of (TOP-REAL 3) st not u is zero & P = Dir u holds
qfconic (1,1,(- 1),0,0,0,u) = 0 }
;
hence
( R is Element of absolute & P <> R )
by A7, PASCAL:def 2; verum