let f be PartFunc of REAL ,REAL ; :: thesis: ( f is convergent_in+infty & f " {0 } = {} & lim_in+infty f <> 0 implies ( f ^ is convergent_in+infty & lim_in+infty (f ^ ) = (lim_in+infty f) " ) )
assume A1:
( f is convergent_in+infty & f " {0 } = {} & lim_in+infty f <> 0 )
; :: thesis: ( f ^ is convergent_in+infty & lim_in+infty (f ^ ) = (lim_in+infty f) " )
then A2: dom f =
(dom f) \ (f " {0 })
.=
dom (f ^ )
by RFUNCT_1:def 8
;
then A3:
for r being Real ex g being Real st
( r < g & g in dom (f ^ ) )
by A1, Def6;
A4:
now let seq be
Real_Sequence;
:: thesis: ( seq is divergent_to+infty & rng seq c= dom (f ^ ) implies ( (f ^ ) /* seq is convergent & lim ((f ^ ) /* seq) = (lim_in+infty f) " ) )assume A5:
(
seq is
divergent_to+infty &
rng seq c= dom (f ^ ) )
;
:: thesis: ( (f ^ ) /* seq is convergent & lim ((f ^ ) /* seq) = (lim_in+infty f) " )then A6:
(
f /* seq is
convergent &
lim (f /* seq) = lim_in+infty f )
by A1, A2, Def12;
then
(f /* seq) " is
convergent
by A1, A5, RFUNCT_2:26, SEQ_2:35;
hence
(f ^ ) /* seq is
convergent
by A5, RFUNCT_2:27;
:: thesis: lim ((f ^ ) /* seq) = (lim_in+infty f) " thus lim ((f ^ ) /* seq) =
lim ((f /* seq) " )
by A5, RFUNCT_2:27
.=
(lim_in+infty f) "
by A1, A5, A6, RFUNCT_2:26, SEQ_2:36
;
:: thesis: verum end;
hence
f ^ is convergent_in+infty
by A3, Def6; :: thesis: lim_in+infty (f ^ ) = (lim_in+infty f) "
hence
lim_in+infty (f ^ ) = (lim_in+infty f) "
by A4, Def12; :: thesis: verum