let x0 be Real; :: thesis: for f being PartFunc of REAL ,REAL st ex r being Real st
( 0 < r & f | ].x0,(x0 + r).[ is non-decreasing & not f | ].x0,(x0 + r).[ is bounded_below ) & ( 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 ; :: thesis: ( ex r being Real st
( 0 < r & f | ].x0,(x0 + r).[ is non-decreasing & not f | ].x0,(x0 + r).[ is bounded_below ) & ( 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:
( 0 < r & f | ].x0,(x0 + r).[ is non-decreasing & not f | ].x0,(x0 + r).[ is bounded_below )
; :: thesis: ( 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 )
; :: thesis: 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 )
; :: according to LIMFUNC2:def 6 :: thesis: 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; :: thesis: ( seq is convergent & lim seq = x0 & rng seq c= (dom f) /\ (right_open_halfline x0) implies f /* seq is divergent_to-infty )
assume A2:
( seq is convergent & lim seq = x0 & rng seq c= (dom f) /\ (right_open_halfline x0) )
; :: thesis: f /* seq is divergent_to-infty
now let t be
Real;
:: thesis: ex n being Element of NAT st
for k being Element of NAT st n <= k holds
(f /* seq) . k < tconsider g1 being
set such that A3:
(
g1 in ].x0,(x0 + r).[ /\ (dom f) &
f . g1 < t )
by A1, RFUNCT_1:88;
reconsider g1 =
g1 as
Real by A3;
g1 in ].x0,(x0 + r).[
by A3, XBOOLE_0:def 4;
then
g1 in { r1 where r1 is Real : ( x0 < r1 & r1 < x0 + r ) }
by RCOMP_1:def 2;
then A4:
ex
r1 being
Real st
(
r1 = g1 &
x0 < r1 &
r1 < x0 + r )
;
then consider n being
Element of
NAT such that A5:
for
k being
Element of
NAT st
n <= k holds
seq . k < g1
by A2, Th2;
take n =
n;
:: thesis: for k being Element of NAT st n <= k holds
(f /* seq) . k < tlet k be
Element of
NAT ;
:: thesis: ( n <= k implies (f /* seq) . k < t )
seq . k in rng seq
by VALUED_0:28;
then A6:
seq . k in (dom f) /\ (right_open_halfline x0)
by A2;
assume
n <= k
;
:: thesis: (f /* seq) . k < tthen A7:
seq . k < g1
by A5;
then A8:
seq . k < x0 + r
by A4, XXREAL_0:2;
A9:
(
(dom f) /\ (right_open_halfline x0) c= dom f &
(dom f) /\ (right_open_halfline x0) c= right_open_halfline x0 )
by XBOOLE_1:17;
then
(
seq . k in dom f &
seq . k in right_open_halfline x0 )
by A6;
then
seq . k in { r2 where r2 is Real : x0 < r2 }
by XXREAL_1:230;
then
ex
r2 being
Real st
(
r2 = seq . k &
x0 < r2 )
;
then
seq . k in { g2 where g2 is Real : ( x0 < g2 & g2 < x0 + r ) }
by A8;
then
seq . k in ].x0,(x0 + r).[
by RCOMP_1:def 2;
then
seq . k in ].x0,(x0 + r).[ /\ (dom f)
by A6, A9, XBOOLE_0:def 4;
then
f . (seq . k) <= f . g1
by A1, A3, A7, RFUNCT_2:45;
then
f . (seq . k) < t
by A3, XXREAL_0:2;
hence
(f /* seq) . k < t
by A2, A9, FUNCT_2:185, XBOOLE_1:1;
:: thesis: verum end;
hence
f /* seq is divergent_to-infty
by LIMFUNC1:def 5; :: thesis: verum