let a be real number ; ex s being Rational_Sequence st
( s is convergent & lim s = a & ( for n being Element of NAT holds s . n <= a ) )
deffunc H1( Element of NAT ) -> Element of REAL = [\(($1 + 1) * a)/] / ($1 + 1);
consider s being Real_Sequence such that
A1:
for n being Element of NAT holds s . n = H1(n)
from SEQ_1:sch 1();
then reconsider s = s as Rational_Sequence by Def6;
deffunc H2( Element of NAT ) -> Element of REAL = 1 / ($1 + 1);
consider s2 being Real_Sequence such that
A2:
for n being Element of NAT holds s2 . n = H2(n)
from SEQ_1:sch 1();
reconsider a1 = a as Real by XREAL_0:def 1;
reconsider s1 = NAT --> a1 as Real_Sequence ;
take
s
; ( s is convergent & lim s = a & ( for n being Element of NAT holds s . n <= a ) )
set s3 = s1 - s2;
A3:
s2 is convergent
by A2, SEQ_4:45;
then A4:
s1 - s2 is convergent
by SEQ_2:25;
lim s2 = 0
by A2, SEQ_4:45;
then A7: lim (s1 - s2) =
(s1 . 0 ) - 0
by A3, SEQ_4:59
.=
a
by FUNCOP_1:13
;
A8: lim s1 =
s1 . 0
by SEQ_4:41
.=
a
by FUNCOP_1:13
;
hence
s is convergent
by A4, A7, A5, SEQ_2:33; ( lim s = a & ( for n being Element of NAT holds s . n <= a ) )
thus
lim s = a
by A4, A7, A8, A5, SEQ_2:34; for n being Element of NAT holds s . n <= a
let n be Element of NAT ; s . n <= a
s . n <= s1 . n
by A5;
hence
s . n <= a
by FUNCOP_1:13; verum