reconsider s2 = NAT --> 1 as Real_Sequence by FUNCOP_1:57;
let s be Real_Sequence; for a being real number st a >= 1 & ( for n being Element of NAT st n >= 1 holds
s . n = n -Root a ) holds
( s is convergent & lim s = 1 )
let a be real number ; ( a >= 1 & ( for n being Element of NAT st n >= 1 holds
s . n = n -Root a ) implies ( s is convergent & lim s = 1 ) )
assume A1:
a >= 1
; ( ex n being Element of NAT st
( n >= 1 & not s . n = n -Root a ) or ( s is convergent & lim s = 1 ) )
deffunc H1( Element of NAT ) -> Element of REAL = (a - 1) / ($1 + 1);
consider s1 being Real_Sequence such that
A2:
for n being Element of NAT holds s1 . n = H1(n)
from SEQ_1:sch 1();
set s3 = s2 + s1;
A3:
s1 is convergent
by A2, SEQ_4:46;
then A4:
s2 + s1 is convergent
by SEQ_2:19;
assume A5:
for n being Element of NAT st n >= 1 holds
s . n = n -Root a
; ( s is convergent & lim s = 1 )
lim s1 = 0
by A2, SEQ_4:46;
then A11: lim (s2 + s1) =
(s2 . 0 ) + 0
by A3, SEQ_4:59
.=
1
by FUNCOP_1:13
;
A12: lim s2 =
s2 . 0
by SEQ_4:41
.=
1
by FUNCOP_1:13
;
then A13:
s ^\ 1 is convergent
by A4, A11, A6, SEQ_2:33;
hence
s is convergent
by SEQ_4:35; lim s = 1
lim (s ^\ 1) = 1
by A4, A11, A12, A6, SEQ_2:34;
hence
lim s = 1
by A13, SEQ_4:36; verum