let r be real number ; :: thesis: for X being set
for f being PartFunc of REAL ,REAL st X c= dom f & f | X is continuous holds
(r (#) f) | X is continuous
let X be set ; :: thesis: for f being PartFunc of REAL ,REAL st X c= dom f & f | X is continuous holds
(r (#) f) | X is continuous
let f be PartFunc of REAL ,REAL ; :: thesis: ( X c= dom f & f | X is continuous implies (r (#) f) | X is continuous )
assume Z:
X c= dom f
; :: thesis: ( not f | X is continuous or (r (#) f) | X is continuous )
assume A1:
f | X is continuous
; :: thesis: (r (#) f) | X is continuous
A3:
X c= dom (r (#) f)
by Z, VALUED_1:def 5;
now let s1 be
Real_Sequence;
:: thesis: ( rng s1 c= X & s1 is convergent & lim s1 in X implies ( (r (#) f) /* s1 is convergent & (r (#) f) . (lim s1) = lim ((r (#) f) /* s1) ) )assume A4:
(
rng s1 c= X &
s1 is
convergent &
lim s1 in X )
;
:: thesis: ( (r (#) f) /* s1 is convergent & (r (#) f) . (lim s1) = lim ((r (#) f) /* s1) )then A5:
(
f /* s1 is
convergent &
f . (lim s1) = lim (f /* s1) )
by A1, Th14, Z;
then A6:
r (#) (f /* s1) is
convergent
by SEQ_2:21;
(r (#) f) . (lim s1) =
r * (lim (f /* s1))
by A3, A4, A5, VALUED_1:def 5
.=
lim (r (#) (f /* s1))
by A5, SEQ_2:22
.=
lim ((r (#) f) /* s1)
by Z, A4, RFUNCT_2:24, XBOOLE_1:1
;
hence
(
(r (#) f) /* s1 is
convergent &
(r (#) f) . (lim s1) = lim ((r (#) f) /* s1) )
by Z, A4, A6, RFUNCT_2:24, XBOOLE_1:1;
:: thesis: verum end;
hence
(r (#) f) | X is continuous
by A3, Th14; :: thesis: verum