let p be Polynomial of F_Complex; ( len p >= 2 implies for r being Real ex e being Real st
for z being Element of F_Complex st e < |.z.| holds
|.(eval (p,z)).| > r )
assume
len p >= 2
; for r being Real ex e being Real st
for z being Element of F_Complex st e < |.z.| holds
|.(eval (p,z)).| > r
per cases then
( len p = 2 or len p > 2 )
by XXREAL_0:1;
suppose A1:
len p = 2
;
for r being Real ex e being Real st
for z being Element of F_Complex st e < |.z.| holds
|.(eval (p,z)).| > rthen A2:
p = <%(p . 0),(p . 1)%>
by Th38;
set N1 =
|.(p . 1).|;
(
p . ((len p) -' 1) <> 0. F_Complex &
(len p) -' 1
= 2
- 1 )
by A1, UPROOTS:18, XREAL_1:233;
then A3:
p . 1
<> 0
by COMPLFLD:def 1;
let r be
Real;
ex e being Real st
for z being Element of F_Complex st e < |.z.| holds
|.(eval (p,z)).| > rtake e =
((|.(p . 1).| ") * |.r.|) + (|.(- (p . 0)).| * (|.(p . 1).| "));
for z being Element of F_Complex st e < |.z.| holds
|.(eval (p,z)).| > rlet z be
Element of
F_Complex;
( e < |.z.| implies |.(eval (p,z)).| > r )assume A4:
e < |.z.|
;
|.(eval (p,z)).| > rA5:
(((|.(p . 1).| ") * |.r.|) + (|.(- (p . 0)).| * (|.(p . 1).| "))) * |.(p . 1).| < |.z.| * |.(p . 1).|
by A4, A3, XREAL_1:68;
A6:
((|.(p . 1).| ") * |.r.|) * |.(p . 1).| =
|.r.| * ((|.(p . 1).| ") * |.(p . 1).|)
.=
|.r.| * 1
by A3, XCMPLX_0:def 7
;
A7:
(|.(- (p . 0)).| * (|.(p . 1).| ")) * |.(p . 1).| =
|.(- (p . 0)).| * ((|.(p . 1).| ") * |.(p . 1).|)
.=
|.(- (p . 0)).| * 1
by A3, XCMPLX_0:def 7
;
(((|.(p . 1).| ") * |.r.|) + (|.(- (p . 0)).| * (|.(p . 1).| "))) * |.(p . 1).| = |.r.| + |.(- (p . 0)).|
by A6, A7;
then A8:
|.r.| < (|.z.| * |.(p . 1).|) - |.(- (p . 0)).|
by A5, XREAL_1:20;
reconsider z1 =
z * (p . 1),
z2 =
- (p . 0) as
Complex ;
A9:
|.(z * (p . 1)).| - |.(- (p . 0)).| <= |.((z * (p . 1)) - (- (p . 0))).|
by COMPLEX1:59;
A10:
(z * (p . 1)) - (- (p . 0)) =
(z * (p . 1)) + (- (- (p . 0)))
.=
(z * (p . 1)) + (p . 0)
;
|.z.| * |.(p . 1).| = |.(z * (p . 1)).|
by COMPLEX1:65;
then
|.r.| < |.((z * (p . 1)) - (- (p . 0))).|
by A8, A9, XXREAL_0:2;
then A11:
|.r.| < |.(eval (p,z)).|
by A2, POLYNOM5:44, A10;
r <= |.r.|
by COMPLEX1:76;
hence
|.(eval (p,z)).| > r
by A11, XXREAL_0:2;
verum end; end;