let X be ComplexUnitarySpace; for z being Complex
for seq being sequence of X st seq is convergent holds
lim (z * seq) = z * (lim seq)
let z be Complex; for seq being sequence of X st seq is convergent holds
lim (z * seq) = z * (lim seq)
let seq be sequence of X; ( seq is convergent implies lim (z * seq) = z * (lim seq) )
set g = lim seq;
set h = z * (lim seq);
A1:
now ( z = 0 implies for r being Real st r > 0 holds
ex k being Nat st
for n being Nat st n >= k holds
dist (((z * seq) . n),(z * (lim seq))) < r )set m1 = the
Nat;
assume A2:
z = 0
;
for r being Real st r > 0 holds
ex k being Nat st
for n being Nat st n >= k holds
dist (((z * seq) . n),(z * (lim seq))) < rlet r be
Real;
( r > 0 implies ex k being Nat st
for n being Nat st n >= k holds
dist (((z * seq) . n),(z * (lim seq))) < r )assume A3:
r > 0
;
ex k being Nat st
for n being Nat st n >= k holds
dist (((z * seq) . n),(z * (lim seq))) < rtake k = the
Nat;
for n being Nat st n >= k holds
dist (((z * seq) . n),(z * (lim seq))) < rlet n be
Nat;
( n >= k implies dist (((z * seq) . n),(z * (lim seq))) < r )assume
n >= k
;
dist (((z * seq) . n),(z * (lim seq))) < r dist (
(z * (seq . n)),
(z * (lim seq))) =
dist (
(0c * (seq . n)),
H1(
X))
by A2, CLVECT_1:1
.=
dist (
H1(
X),
H1(
X))
by CLVECT_1:1
.=
0
by CSSPACE:50
;
hence
dist (
((z * seq) . n),
(z * (lim seq)))
< r
by A3, CLVECT_1:def 14;
verum end;
assume A4:
seq is convergent
; lim (z * seq) = z * (lim seq)
A5:
now ( z <> 0 implies for r being Real st r > 0 holds
ex k being Nat st
for n being Nat st n >= k holds
dist (((z * seq) . n),(z * (lim seq))) < r )A6:
0 / |.z.| = 0
;
assume A7:
z <> 0
;
for r being Real st r > 0 holds
ex k being Nat st
for n being Nat st n >= k holds
dist (((z * seq) . n),(z * (lim seq))) < rthen A8:
|.z.| > 0
by COMPLEX1:47;
let r be
Real;
( r > 0 implies ex k being Nat st
for n being Nat st n >= k holds
dist (((z * seq) . n),(z * (lim seq))) < r )assume
r > 0
;
ex k being Nat st
for n being Nat st n >= k holds
dist (((z * seq) . n),(z * (lim seq))) < rthen
r / |.z.| > 0
by A8, A6, XREAL_1:74;
then consider m1 being
Nat such that A9:
for
n being
Nat st
n >= m1 holds
dist (
(seq . n),
(lim seq))
< r / |.z.|
by A4, Def2;
take k =
m1;
for n being Nat st n >= k holds
dist (((z * seq) . n),(z * (lim seq))) < rlet n be
Nat;
( n >= k implies dist (((z * seq) . n),(z * (lim seq))) < r )assume
n >= k
;
dist (((z * seq) . n),(z * (lim seq))) < rthen A10:
dist (
(seq . n),
(lim seq))
< r / |.z.|
by A9;
A11:
|.z.| <> 0
by A7, COMPLEX1:47;
A12:
|.z.| * (r / |.z.|) =
|.z.| * ((|.z.| ") * r)
by XCMPLX_0:def 9
.=
(|.z.| * (|.z.| ")) * r
.=
1
* r
by A11, XCMPLX_0:def 7
.=
r
;
dist (
(z * (seq . n)),
(z * (lim seq))) =
||.((z * (seq . n)) - (z * (lim seq))).||
by CSSPACE:def 16
.=
||.(z * ((seq . n) - (lim seq))).||
by CLVECT_1:9
.=
|.z.| * ||.((seq . n) - (lim seq)).||
by CSSPACE:43
.=
|.z.| * (dist ((seq . n),(lim seq)))
by CSSPACE:def 16
;
then
dist (
(z * (seq . n)),
(z * (lim seq)))
< r
by A8, A10, A12, XREAL_1:68;
hence
dist (
((z * seq) . n),
(z * (lim seq)))
< r
by CLVECT_1:def 14;
verum end;
z * seq is convergent
by A4, Th5;
hence
lim (z * seq) = z * (lim seq)
by A1, A5, Def2; verum