let x0 be Real; :: thesis: for f1, f2 being PartFunc of REAL ,REAL st f1 is_divergent_to+infty_in x0 & ( for r1, r2 being Real st r1 < x0 & x0 < r2 holds
ex g1, g2 being Real st
( r1 < g1 & g1 < x0 & g1 in dom (f1 + f2) & g2 < r2 & x0 < g2 & g2 in dom (f1 + f2) ) ) & ex r being Real st
( 0 < r & f2 | (].(x0 - r),x0.[ \/ ].x0,(x0 + r).[) is bounded_below ) holds
f1 + f2 is_divergent_to+infty_in x0
let f1, f2 be PartFunc of REAL ,REAL ; :: thesis: ( f1 is_divergent_to+infty_in x0 & ( for r1, r2 being Real st r1 < x0 & x0 < r2 holds
ex g1, g2 being Real st
( r1 < g1 & g1 < x0 & g1 in dom (f1 + f2) & g2 < r2 & x0 < g2 & g2 in dom (f1 + f2) ) ) & ex r being Real st
( 0 < r & f2 | (].(x0 - r),x0.[ \/ ].x0,(x0 + r).[) is bounded_below ) implies f1 + f2 is_divergent_to+infty_in x0 )
assume A1:
( f1 is_divergent_to+infty_in x0 & ( for r1, r2 being Real st r1 < x0 & x0 < r2 holds
ex g1, g2 being Real st
( r1 < g1 & g1 < x0 & g1 in dom (f1 + f2) & g2 < r2 & x0 < g2 & g2 in dom (f1 + f2) ) ) )
; :: thesis: ( for r being Real holds
( not 0 < r or not f2 | (].(x0 - r),x0.[ \/ ].x0,(x0 + r).[) is bounded_below ) or f1 + f2 is_divergent_to+infty_in x0 )
given r being Real such that A2:
( 0 < r & f2 | (].(x0 - r),x0.[ \/ ].x0,(x0 + r).[) is bounded_below )
; :: thesis: f1 + f2 is_divergent_to+infty_in x0
now let s be
Real_Sequence;
:: thesis: ( s is convergent & lim s = x0 & rng s c= (dom (f1 + f2)) \ {x0} implies (f1 + f2) /* s is divergent_to+infty )assume A3:
(
s is
convergent &
lim s = x0 &
rng s c= (dom (f1 + f2)) \ {x0} )
;
:: thesis: (f1 + f2) /* s is divergent_to+infty then consider k being
Element of
NAT such that A4:
for
n being
Element of
NAT st
k <= n holds
(
x0 - r < s . n &
s . n < x0 + r )
by A2, Th7;
A5:
(
s ^\ k is
convergent &
lim (s ^\ k) = x0 )
by A3, SEQ_4:33;
rng (s ^\ k) c= rng s
by VALUED_0:21;
then A6:
rng (s ^\ k) c= (dom (f1 + f2)) \ {x0}
by A3, XBOOLE_1:1;
then A7:
(
rng (s ^\ k) c= dom (f1 + f2) &
rng (s ^\ k) c= dom f1 &
rng (s ^\ k) c= dom f2 &
rng (s ^\ k) c= (dom f1) \ {x0} )
by Lm4;
then A8:
f1 /* (s ^\ k) is
divergent_to+infty
by A1, A5, Def2;
A9:
rng (s ^\ k) c= (dom f1) /\ (dom f2)
by A7, VALUED_1:def 1;
A10:
rng s c= dom (f1 + f2)
by A3, Lm4;
now consider r1 being
real number such that A11:
for
g being
set st
g in (].(x0 - r),x0.[ \/ ].x0,(x0 + r).[) /\ (dom f2) holds
r1 <= f2 . g
by A2, RFUNCT_1:88;
take r2 =
r1 - 1;
:: thesis: for n being Element of NAT holds r2 < (f2 /* (s ^\ k)) . nlet n be
Element of
NAT ;
:: thesis: r2 < (f2 /* (s ^\ k)) . n
k <= n + k
by NAT_1:12;
then
(
x0 - r < s . (n + k) &
s . (n + k) < x0 + r )
by A4;
then
(
x0 - r < (s ^\ k) . n &
(s ^\ k) . n < x0 + r )
by NAT_1:def 3;
then
(s ^\ k) . n in { g2 where g2 is Real : ( x0 - r < g2 & g2 < x0 + r ) }
;
then A12:
(s ^\ k) . n in ].(x0 - r),(x0 + r).[
by RCOMP_1:def 2;
A13:
(s ^\ k) . n in rng (s ^\ k)
by VALUED_0:28;
then
not
(s ^\ k) . n in {x0}
by A6, XBOOLE_0:def 5;
then
(s ^\ k) . n in ].(x0 - r),(x0 + r).[ \ {x0}
by A12, XBOOLE_0:def 5;
then
(s ^\ k) . n in ].(x0 - r),x0.[ \/ ].x0,(x0 + r).[
by A2, Th4;
then
(s ^\ k) . n in (].(x0 - r),x0.[ \/ ].x0,(x0 + r).[) /\ (dom f2)
by A7, A13, XBOOLE_0:def 4;
then
r1 <= f2 . ((s ^\ k) . n)
by A11;
then
r1 - 1
< (f2 . ((s ^\ k) . n)) - 0
by XREAL_1:17;
hence
r2 < (f2 /* (s ^\ k)) . n
by A7, FUNCT_2:185;
:: thesis: verum end; then
f2 /* (s ^\ k) is
bounded_below
by SEQ_2:def 4;
then A14:
(f1 /* (s ^\ k)) + (f2 /* (s ^\ k)) is
divergent_to+infty
by A8, LIMFUNC1:36;
(f1 /* (s ^\ k)) + (f2 /* (s ^\ k)) =
(f1 + f2) /* (s ^\ k)
by A9, RFUNCT_2:23
.=
((f1 + f2) /* s) ^\ k
by A10, VALUED_0:27
;
hence
(f1 + f2) /* s is
divergent_to+infty
by A14, LIMFUNC1:34;
:: thesis: verum end;
hence
f1 + f2 is_divergent_to+infty_in x0
by A1, Def2; :: thesis: verum