let x0 be Real; for f being PartFunc of REAL,REAL st ex r being Real st
( f | ].x0,(x0 + r).[ is non-increasing & not f | ].x0,(x0 + r).[ is bounded_above ) & ( for r being Real st x0 < r holds
ex g being Real st
( g < r & x0 < g & g in dom f ) ) holds
f is_right_divergent_to+infty_in x0
let f be PartFunc of REAL,REAL; ( ex r being Real st
( f | ].x0,(x0 + r).[ is non-increasing & not f | ].x0,(x0 + r).[ is bounded_above ) & ( for r being Real st x0 < r holds
ex g being Real st
( g < r & x0 < g & g in dom f ) ) implies f is_right_divergent_to+infty_in x0 )
given r being Real such that A1:
f | ].x0,(x0 + r).[ is non-increasing
and
A2:
not f | ].x0,(x0 + r).[ is bounded_above
; ( ex r being Real st
( x0 < r & ( for g being Real holds
( not g < r or not x0 < g or not g in dom f ) ) ) or f is_right_divergent_to+infty_in x0 )
assume
for r being Real st x0 < r holds
ex g being Real st
( g < r & x0 < g & g in dom f )
; f is_right_divergent_to+infty_in x0
hence
for r being Real st x0 < r holds
ex g being Real st
( g < r & x0 < g & g in dom f )
; LIMFUNC2:def 5 for seq being Real_Sequence st seq is convergent & lim seq = x0 & rng seq c= (dom f) /\ (right_open_halfline x0) holds
f /* seq is divergent_to+infty
let seq be Real_Sequence; ( seq is convergent & lim seq = x0 & rng seq c= (dom f) /\ (right_open_halfline x0) implies f /* seq is divergent_to+infty )
assume that
A3:
seq is convergent
and
A4:
lim seq = x0
and
A5:
rng seq c= (dom f) /\ (right_open_halfline x0)
; f /* seq is divergent_to+infty
now for t being Real ex n being Nat st
for k being Nat st n <= k holds
t < (f /* seq) . klet t be
Real;
ex n being Nat st
for k being Nat st n <= k holds
t < (f /* seq) . kA6:
(dom f) /\ (right_open_halfline x0) c= dom f
by XBOOLE_1:17;
consider g1 being
object such that A7:
g1 in ].x0,(x0 + r).[ /\ (dom f)
and A8:
t < f . g1
by A2, RFUNCT_1:70;
reconsider g1 =
g1 as
Real by A7;
g1 in ].x0,(x0 + r).[
by A7, XBOOLE_0:def 4;
then
g1 in { r1 where r1 is Real : ( x0 < r1 & r1 < x0 + r ) }
by RCOMP_1:def 2;
then A9:
ex
r1 being
Real st
(
r1 = g1 &
x0 < r1 &
r1 < x0 + r )
;
then consider n being
Nat such that A10:
for
k being
Nat st
n <= k holds
seq . k < g1
by A3, A4, Th2;
take n =
n;
for k being Nat st n <= k holds
t < (f /* seq) . klet k be
Nat;
( n <= k implies t < (f /* seq) . k )
seq . k in rng seq
by VALUED_0:28;
then A11:
seq . k in (dom f) /\ (right_open_halfline x0)
by A5;
(dom f) /\ (right_open_halfline x0) c= right_open_halfline x0
by XBOOLE_1:17;
then
seq . k in right_open_halfline x0
by A11;
then
seq . k in { r2 where r2 is Real : x0 < r2 }
by XXREAL_1:230;
then A12:
ex
r2 being
Real st
(
r2 = seq . k &
x0 < r2 )
;
A13:
k in NAT
by ORDINAL1:def 12;
assume
n <= k
;
t < (f /* seq) . kthen A14:
seq . k < g1
by A10;
then
seq . k < x0 + r
by A9, XXREAL_0:2;
then
seq . k in { g2 where g2 is Real : ( x0 < g2 & g2 < x0 + r ) }
by A12;
then
seq . k in ].x0,(x0 + r).[
by RCOMP_1:def 2;
then
seq . k in ].x0,(x0 + r).[ /\ (dom f)
by A11, A6, XBOOLE_0:def 4;
then
f . g1 <= f . (seq . k)
by A1, A7, A14, RFUNCT_2:23;
then
t < f . (seq . k)
by A8, XXREAL_0:2;
hence
t < (f /* seq) . k
by A5, A6, FUNCT_2:108, XBOOLE_1:1, A13;
verum end;
hence
f /* seq is divergent_to+infty
; verum