let x0 be real number ; :: thesis: for S being RealNormSpace
for f1 being PartFunc of REAL, the carrier of S
for f2 being PartFunc of the carrier of S,REAL st x0 in dom (f2 * f1) & f1 is_continuous_in x0 & f2 is_continuous_in f1 /. x0 holds
f2 * f1 is_continuous_in x0
let S be RealNormSpace; :: thesis: for f1 being PartFunc of REAL, the carrier of S
for f2 being PartFunc of the carrier of S,REAL st x0 in dom (f2 * f1) & f1 is_continuous_in x0 & f2 is_continuous_in f1 /. x0 holds
f2 * f1 is_continuous_in x0
let f1 be PartFunc of REAL, the carrier of S; :: thesis: for f2 being PartFunc of the carrier of S,REAL st x0 in dom (f2 * f1) & f1 is_continuous_in x0 & f2 is_continuous_in f1 /. x0 holds
f2 * f1 is_continuous_in x0
let f2 be PartFunc of the carrier of S,REAL; :: thesis: ( x0 in dom (f2 * f1) & f1 is_continuous_in x0 & f2 is_continuous_in f1 /. x0 implies f2 * f1 is_continuous_in x0 )
assume A1: x0 in dom (f2 * f1) ; :: thesis: ( not f1 is_continuous_in x0 or not f2 is_continuous_in f1 /. x0 or f2 * f1 is_continuous_in x0 )
assume that
A2: f1 is_continuous_in x0 and
A3: f2 is_continuous_in f1 /. x0 ; :: thesis: f2 * f1 is_continuous_in x0
let s1 be Real_Sequence; :: according to FCONT_1:def 1 :: thesis: ( not rng s1 c= dom (f2 * f1) or not s1 is convergent or not lim s1 = x0 or ( (f2 * f1) /* s1 is convergent & (f2 * f1) . x0 = lim ((f2 * f1) /* s1) ) )
assume that
A4: rng s1 c= dom (f2 * f1) and
A5: ( s1 is convergent & lim s1 = x0 ) ; :: thesis: ( (f2 * f1) /* s1 is convergent & (f2 * f1) . x0 = lim ((f2 * f1) /* s1) )
A6: dom (f2 * f1) c= dom f1 by RELAT_1:25;
A8: rng (f1 /* s1) c= dom f2

proof

let x be set ; :: according to TARSKI:def 3 :: thesis: ( not x in rng (f1 /* s1) or x in dom f2 )
assume x in rng (f1 /* s1) ; :: thesis: x in dom f2
then consider n being Element of NAT such that
A7: x = (f1 /* s1) . n by FUNCT_2:113;
s1 . n in rng s1 by VALUED_0:28;
then f1 . (s1 . n) in dom f2 by A4, FUNCT_1:11;
hence x in dom f2 by A4, A6, A7, FUNCT_2:108, XBOOLE_1:1; :: thesis: verum

end;

aa: now

let n be Element of NAT ; :: thesis: ((f2 * f1) /* s1) . n = (f2 /* (f1 /* s1)) . n
s1 . n in rng s1 by VALUED_0:28;
then A9: s1 . n in dom f1 by A4, FUNCT_1:11;
thus ((f2 * f1) /* s1) . n = (f2 * f1) . (s1 . n) by A4, FUNCT_2:108
.= f2 . (f1 . (s1 . n)) by A9, FUNCT_1:13
.= f2 . ((f1 /* s1) . n) by A4, A6, FUNCT_2:108, XBOOLE_1:1
.= (f2 /* (f1 /* s1)) . n by A8, FUNCT_2:108 ; :: thesis: verum

end;

then A10: f2 /* (f1 /* s1) = (f2 * f1) /* s1 by FUNCT_2:63;
rng s1 c= dom f1 by A4, A6, XBOOLE_1:1;
then A11: ( f1 /* s1 is convergent & f1 /. x0 = lim (f1 /* s1) ) by A2, A5, NFCONT_3:def 1;
hence (f2 * f1) /* s1 is convergent by A3, A8, A10, NFCONT_1:def 6; :: thesis: (f2 * f1) . x0 = lim ((f2 * f1) /* s1)
thus (f2 * f1) . x0 = (f2 * f1) /. x0 by A1, PARTFUN1:def 6
.= f2 /. (f1 /. x0) by A1, PARTFUN2:3
.= lim (f2 /* (f1 /* s1)) by A11, A3, A8, NFCONT_1:def 6
.= lim ((f2 * f1) /* s1) by aa, FUNCT_2:63 ; :: thesis: verum