let x be Element of F_Complex; for n being Nat ex f being Function of COMPLEX,COMPLEX st
( f = FPower (x,n) & f is_continuous_on COMPLEX )
defpred S1[ 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 Nat st S1[n] holds
S1[n + 1]
proof
let n be
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 Th69;
hence
g is_continuous_on COMPLEX
by A3, Th62, CFCONT_1:43;
verum
end;
A4:
S1[ 0 ]
thus
for n being Nat holds S1[n]
from NAT_1:sch 2(A4, A2); verum