let x0 be Real; :: thesis: for f being PartFunc of REAL ,REAL st f is_right_convergent_in x0 & lim_right f,x0 = 0 & ( for r being Real st x0 < r holds
ex g being Real st
( g < r & x0 < g & g in dom f & f . g <> 0 ) ) & ex r being Real st
( 0 < r & ( for g being Real st g in (dom f) /\ ].x0,(x0 + r).[ holds
f . g <= 0 ) ) holds
f ^ is_right_divergent_to-infty_in x0
let f be PartFunc of REAL ,REAL ; :: thesis: ( f is_right_convergent_in x0 & lim_right f,x0 = 0 & ( for r being Real st x0 < r holds
ex g being Real st
( g < r & x0 < g & g in dom f & f . g <> 0 ) ) & ex r being Real st
( 0 < r & ( for g being Real st g in (dom f) /\ ].x0,(x0 + r).[ holds
f . g <= 0 ) ) implies f ^ is_right_divergent_to-infty_in x0 )
assume A1:
( f is_right_convergent_in x0 & lim_right f,x0 = 0 & ( for r being Real st x0 < r holds
ex g being Real st
( g < r & x0 < g & g in dom f & f . g <> 0 ) ) )
; :: thesis: ( for r being Real holds
( not 0 < r or ex g being Real st
( g in (dom f) /\ ].x0,(x0 + r).[ & not f . g <= 0 ) ) or f ^ is_right_divergent_to-infty_in x0 )
given r being Real such that A2:
( 0 < r & ( for g being Real st g in (dom f) /\ ].x0,(x0 + r).[ holds
f . g <= 0 ) )
; :: thesis: f ^ is_right_divergent_to-infty_in x0
thus
for r1 being Real st x0 < r1 holds
ex g1 being Real st
( g1 < r1 & x0 < g1 & g1 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 s be Real_Sequence; :: thesis: ( s is convergent & lim s = x0 & rng s c= (dom (f ^ )) /\ (right_open_halfline x0) implies (f ^ ) /* s is divergent_to-infty )
assume A4:
( s is convergent & lim s = x0 & rng s c= (dom (f ^ )) /\ (right_open_halfline x0) )
; :: thesis: (f ^ ) /* s is divergent_to-infty
x0 < x0 + r
by A2, Lm1;
then consider k being Element of NAT such that
A5:
for n being Element of NAT st k <= n holds
s . n < x0 + r
by A4, Th2;
A6:
( s ^\ k is convergent & lim (s ^\ k) = x0 )
by A4, SEQ_4:33;
A7:
( (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 A8:
( rng s c= dom (f ^ ) & rng s c= right_open_halfline x0 )
by A4, XBOOLE_1:1;
dom (f ^ ) = (dom f) \ (f " {0 })
by RFUNCT_1:def 8;
then A9:
dom (f ^ ) c= dom f
by XBOOLE_1:36;
then A10:
rng s c= dom f
by A8, XBOOLE_1:1;
A11:
rng (s ^\ k) c= rng s
by VALUED_0:21;
then A12:
( rng (s ^\ k) c= (dom (f ^ )) /\ (right_open_halfline x0) & rng (s ^\ k) c= dom (f ^ ) & rng (s ^\ k) c= right_open_halfline x0 & rng (s ^\ k) c= dom f )
by A4, A8, A10, XBOOLE_1:1;
then
rng (s ^\ k) c= (dom f) /\ (right_open_halfline x0)
by XBOOLE_1:19;
then A13:
( f /* (s ^\ k) is convergent & lim (f /* (s ^\ k)) = 0 )
by A1, A6, Def8;
A14:
f /* (s ^\ k) is non-zero
by A8, A11, RFUNCT_2:26, XBOOLE_1:1;
A15:
now let n be
Element of
NAT ;
:: thesis: (f /* (s ^\ k)) . n < 0 A16:
(s ^\ k) . n in rng (s ^\ k)
by VALUED_0:28;
then
(s ^\ k) . n in right_open_halfline x0
by A12;
then
(s ^\ k) . n in { g1 where g1 is Real : x0 < g1 }
by XXREAL_1:230;
then A17:
ex
g1 being
Real st
(
g1 = (s ^\ k) . n &
x0 < g1 )
;
s . (n + k) < x0 + r
by A5, NAT_1:12;
then
(s ^\ k) . n < x0 + r
by NAT_1:def 3;
then
(s ^\ k) . n in { g2 where g2 is Real : ( x0 < g2 & g2 < x0 + r ) }
by A17;
then
(s ^\ k) . n in ].x0,(x0 + r).[
by RCOMP_1:def 2;
then
(s ^\ k) . n in (dom f) /\ ].x0,(x0 + r).[
by A12, A16, XBOOLE_0:def 4;
then A18:
f . ((s ^\ k) . n) <= 0
by A2;
(f /* (s ^\ k)) . n <> 0
by A14, SEQ_1:7;
hence
(f /* (s ^\ k)) . n < 0
by A10, A11, A18, FUNCT_2:185, XBOOLE_1:1;
:: thesis: verum end;
then
for n being Element of NAT holds 0 <> (f /* (s ^\ k)) . n
;
then A19:
f /* (s ^\ k) is non-zero
by SEQ_1:7;
for n being Element of NAT st 0 <= n holds
(f /* (s ^\ k)) . n < 0
by A15;
then A20:
(f /* (s ^\ k)) " is divergent_to-infty
by A13, A19, LIMFUNC1:63;
(f /* (s ^\ k)) " =
((f /* s) ^\ k) "
by A8, A9, VALUED_0:27, XBOOLE_1:1
.=
((f /* s) " ) ^\ k
by SEQM_3:41
.=
((f ^ ) /* s) ^\ k
by A4, A7, RFUNCT_2:27, XBOOLE_1:1
;
hence
(f ^ ) /* s is divergent_to-infty
by A20, LIMFUNC1:34; :: thesis: verum