let Rseq be Function of [:NAT,NAT:],REAL; ( Rseq is non-increasing & Rseq is P-convergent implies ( Rseq is bounded_below & Rseq is bounded_above ) )
assume a1:
( Rseq is non-increasing & Rseq is P-convergent )
; ( Rseq is bounded_below & Rseq is bounded_above )
then consider p being Real such that
a3:
for e being Real st 0 < e holds
ex N being Nat st
for n, m being Nat st n >= N & m >= N holds
|.((Rseq . (n,m)) - p).| < e
;
consider N being Nat such that
a4:
for n, m being Nat st n >= N & m >= N holds
|.((Rseq . (n,m)) - p).| < 1
by a3;
a5:
for n, m being Nat st n >= N & m >= N holds
|.(Rseq . (n,m)).| < 1 + |.p.|
deffunc H1( Element of NAT ) -> object = |.(Rseq . (1,c1)).|;
deffunc H2( Element of NAT ) -> Element of NAT = c1;
reconsider E2 = { H2(m) where m is Element of NAT : m <= N } as non empty finite Subset of NAT from ASYMPT_0:sch 2();
reconsider EE = [:E2,E2:] as finite set ;
c1:
E2 is finite
;
deffunc H3( Element of NAT , Element of NAT ) -> object = |.(Rseq . (c1,c2)).|;
a9:
{ H3(m,n) where m, n is Element of NAT : ( m in E2 & n in E2 ) } is finite
from FRAENKEL:sch 22(c1, c1);
set F = { H3(m,n) where m, n is Element of NAT : ( m in E2 & n in E2 ) } ;
N is Element of NAT
by ORDINAL1:def 12;
then
N in E2
;
then b1:
|.(Rseq . (N,N)).| in { H3(m,n) where m, n is Element of NAT : ( m in E2 & n in E2 ) }
;
then reconsider F = { H3(m,n) where m, n is Element of NAT : ( m in E2 & n in E2 ) } as non empty real-membered set by b1, MEMBERED:def 3;
reconsider M1 = sup F as Element of REAL by a9, XXREAL_2:16;
set M = max (M1,(1 + |.p.|));
a14:
( max (M1,(1 + |.p.|)) >= 1 + |.p.| & 1 + |.p.| >= 1 & max (M1,(1 + |.p.|)) >= M1 & max (M1,(1 + |.p.|)) >= M1 )
by XXREAL_0:25, XREAL_1:31, COMPLEX1:46;
c1:
for n, m being Nat holds |.(Rseq . (n,m)).| <= max (M1,(1 + |.p.|))
now for a being ExtReal st a in Rseq .: [:NAT,NAT:] holds
( - (max (M1,(1 + |.p.|))) <= a & a <= max (M1,(1 + |.p.|)) )let a be
ExtReal;
( a in Rseq .: [:NAT,NAT:] implies ( - (max (M1,(1 + |.p.|))) <= a & a <= max (M1,(1 + |.p.|)) ) )assume
a in Rseq .: [:NAT,NAT:]
;
( - (max (M1,(1 + |.p.|))) <= a & a <= max (M1,(1 + |.p.|)) )then consider x being
Element of
[:NAT,NAT:] such that b2:
(
x in [:NAT,NAT:] &
a = Rseq . x )
by FUNCT_2:65;
consider n,
m being
object such that b3:
(
n in NAT &
m in NAT &
x = [n,m] )
by ZFMISC_1:def 2;
reconsider n =
n,
m =
m as
Element of
NAT by b3;
|.(Rseq . (n,m)).| <= max (
M1,
(1 + |.p.|))
by c1;
hence
(
- (max (M1,(1 + |.p.|))) <= a &
a <= max (
M1,
(1 + |.p.|)) )
by b3, b2, ABSVALUE:5;
verum end;
then
( ( for a being ExtReal st a in Rseq .: [:NAT,NAT:] holds
- (max (M1,(1 + |.p.|))) <= a ) & ( for a being ExtReal st a in Rseq .: [:NAT,NAT:] holds
a <= max (M1,(1 + |.p.|)) ) )
;
then
( - (max (M1,(1 + |.p.|))) is LowerBound of Rseq .: [:NAT,NAT:] & max (M1,(1 + |.p.|)) is UpperBound of Rseq .: [:NAT,NAT:] )
by XXREAL_2:def 1, XXREAL_2:def 2;
hence
( Rseq is bounded_below & Rseq is bounded_above )
by XXREAL_2:def 9, XXREAL_2:def 10; verum