let x0 be Real; for f1, f2 being PartFunc of REAL ,REAL st f1 is_right_convergent_in x0 & f2 is_right_divergent_to-infty_in lim_right f1,x0 & ( for r being Real st x0 < r holds
ex g being Real st
( g < r & x0 < g & g in dom (f2 * f1) ) ) & ex g being Real st
( 0 < g & ( for r being Real st r in (dom f1) /\ ].x0,(x0 + g).[ holds
lim_right f1,x0 < f1 . r ) ) holds
f2 * f1 is_right_divergent_to-infty_in x0
let f1, f2 be PartFunc of REAL ,REAL ; ( f1 is_right_convergent_in x0 & f2 is_right_divergent_to-infty_in lim_right f1,x0 & ( for r being Real st x0 < r holds
ex g being Real st
( g < r & x0 < g & g in dom (f2 * f1) ) ) & ex g being Real st
( 0 < g & ( for r being Real st r in (dom f1) /\ ].x0,(x0 + g).[ holds
lim_right f1,x0 < f1 . r ) ) implies f2 * f1 is_right_divergent_to-infty_in x0 )
assume that
A1:
f1 is_right_convergent_in x0
and
A2:
f2 is_right_divergent_to-infty_in lim_right f1,x0
and
A3:
for r being Real st x0 < r holds
ex g being Real st
( g < r & x0 < g & g in dom (f2 * f1) )
; ( for g being Real holds
( not 0 < g or ex r being Real st
( r in (dom f1) /\ ].x0,(x0 + g).[ & not lim_right f1,x0 < f1 . r ) ) or f2 * f1 is_right_divergent_to-infty_in x0 )
given g being Real such that A4:
0 < g
and
A5:
for r being Real st r in (dom f1) /\ ].x0,(x0 + g).[ holds
lim_right f1,x0 < f1 . r
; f2 * f1 is_right_divergent_to-infty_in x0
now let s be
Real_Sequence;
( s is convergent & lim s = x0 & rng s c= (dom (f2 * f1)) /\ (right_open_halfline x0) implies (f2 * f1) /* s is divergent_to-infty )assume that A6:
(
s is
convergent &
lim s = x0 )
and A7:
rng s c= (dom (f2 * f1)) /\ (right_open_halfline x0)
;
(f2 * f1) /* s is divergent_to-infty consider k being
Element of
NAT such that A8:
for
n being
Element of
NAT st
k <= n holds
s . n < x0 + g
by A4, A6, Lm1, LIMFUNC2:2;
set q =
(f1 /* s) ^\ k;
A9:
rng s c= dom (f2 * f1)
by A7, Th1;
rng (f1 /* s) c= dom f2
by A7, Th1;
then A10:
f2 /* ((f1 /* s) ^\ k) =
(f2 /* (f1 /* s)) ^\ k
by VALUED_0:27
.=
((f2 * f1) /* s) ^\ k
by A9, VALUED_0:31
;
A11:
rng s c= (dom f1) /\ (right_open_halfline x0)
by A7, Th1;
then A12:
f1 /* s is
convergent
by A1, A2, A6, LIMFUNC2:def 8;
A13:
rng s c= dom f1
by A7, Th1;
A14:
rng s c= right_open_halfline x0
by A7, Th1;
now let x be
set ;
( x in rng ((f1 /* s) ^\ k) implies x in (dom f2) /\ (right_open_halfline (lim_right f1,x0)) )assume
x in rng ((f1 /* s) ^\ k)
;
x in (dom f2) /\ (right_open_halfline (lim_right f1,x0))then consider n being
Element of
NAT such that A15:
((f1 /* s) ^\ k) . n = x
by FUNCT_2:190;
A16:
f1 . (s . (n + k)) =
(f1 /* s) . (n + k)
by A13, FUNCT_2:185
.=
x
by A15, NAT_1:def 3
;
A17:
s . (n + k) < x0 + g
by A8, NAT_1:12;
A18:
s . (n + k) in rng s
by VALUED_0:28;
then
s . (n + k) in right_open_halfline x0
by A14;
then
s . (n + k) in { g1 where g1 is Real : x0 < g1 }
by XXREAL_1:230;
then
ex
g1 being
Real st
(
g1 = s . (n + k) &
x0 < g1 )
;
then
s . (n + k) in { g2 where g2 is Real : ( x0 < g2 & g2 < x0 + g ) }
by A17;
then
s . (n + k) in ].x0,(x0 + g).[
by RCOMP_1:def 2;
then
s . (n + k) in (dom f1) /\ ].x0,(x0 + g).[
by A13, A18, XBOOLE_0:def 4;
then
lim_right f1,
x0 < f1 . (s . (n + k))
by A5;
then
f1 . (s . (n + k)) in { r1 where r1 is Real : lim_right f1,x0 < r1 }
;
then A19:
f1 . (s . (n + k)) in right_open_halfline (lim_right f1,x0)
by XXREAL_1:230;
f1 . (s . (n + k)) in dom f2
by A9, A18, FUNCT_1:21;
hence
x in (dom f2) /\ (right_open_halfline (lim_right f1,x0))
by A19, A16, XBOOLE_0:def 4;
verum end; then A20:
rng ((f1 /* s) ^\ k) c= (dom f2) /\ (right_open_halfline (lim_right f1,x0))
by TARSKI:def 3;
lim (f1 /* s) = lim_right f1,
x0
by A1, A6, A11, LIMFUNC2:def 8;
then
lim ((f1 /* s) ^\ k) = lim_right f1,
x0
by A12, SEQ_4:33;
then
f2 /* ((f1 /* s) ^\ k) is
divergent_to-infty
by A2, A12, A20, LIMFUNC2:def 6;
hence
(f2 * f1) /* s is
divergent_to-infty
by A10, LIMFUNC1:34;
verum end;
hence
f2 * f1 is_right_divergent_to-infty_in x0
by A3, LIMFUNC2:def 6; verum