let x be Element of F_Complex ; for n being Element of NAT ex f being Function of COMPLEX ,COMPLEX st
( f = FPower x,n & f is_continuous_on COMPLEX )
defpred S1[ Element of NAT ] means ex f being Function of COMPLEX ,COMPLEX st
( f = FPower x,$1 & f is_continuous_on COMPLEX );
A1:
the carrier of F_Complex = COMPLEX
by COMPLFLD:def 1;
A2:
for n being Element of NAT st S1[n] holds
S1[n + 1]
proof
let n be
Element of
NAT ;
( S1[n] implies S1[n + 1] )
reconsider g =
FPower x,
(n + 1) as
Function of
COMPLEX ,
COMPLEX by A1;
given f being
Function of
COMPLEX ,
COMPLEX such that A3:
(
f = FPower x,
n &
f is_continuous_on COMPLEX )
;
S1[n + 1]
take
g
;
( g = FPower x,(n + 1) & g is_continuous_on COMPLEX )
thus
g = FPower x,
(n + 1)
;
g is_continuous_on COMPLEX
ex
f1 being
Function of
COMPLEX ,
COMPLEX st
(
f1 = FPower x,
n &
FPower x,
(n + 1) = f1 (#) (id COMPLEX ) )
by Th70;
hence
g is_continuous_on COMPLEX
by A3, Th63, CFCONT_1:65;
verum
end;
A4:
S1[ 0 ]
thus
for n being Element of NAT holds S1[n]
from NAT_1:sch 1(A4, A2); verum