let r, x be Real; ( r > 0 implies ( Partial_Sums (Maclaurin (sin,].(- r),r.[,x)) is convergent & sin . x = Sum (Maclaurin (sin,].(- r),r.[,x)) & Partial_Sums (Maclaurin (cos,].(- r),r.[,x)) is convergent & cos . x = Sum (Maclaurin (cos,].(- r),r.[,x)) ) )
assume A1:
r > 0
; ( Partial_Sums (Maclaurin (sin,].(- r),r.[,x)) is convergent & sin . x = Sum (Maclaurin (sin,].(- r),r.[,x)) & Partial_Sums (Maclaurin (cos,].(- r),r.[,x)) is convergent & cos . x = Sum (Maclaurin (cos,].(- r),r.[,x)) )
set g = sin . x;
Sum (x P_sin) = sin . x
by SIN_COS:40;
then A2:
lim (Partial_Sums (x P_sin)) = sin . x
by SERIES_1:def 3;
A3:
Partial_Sums (x P_sin) is convergent
by SIN_COS:39;
A4:
for p being real number st p > 0 holds
ex n1 being Element of NAT st
for m1 being Element of NAT st m1 >= n1 holds
abs (((Partial_Sums (Maclaurin (sin,].(- r),r.[,x))) . m1) - (sin . x)) < p
proof
let p be
real number ;
( p > 0 implies ex n1 being Element of NAT st
for m1 being Element of NAT st m1 >= n1 holds
abs (((Partial_Sums (Maclaurin (sin,].(- r),r.[,x))) . m1) - (sin . x)) < p )
assume
p > 0
;
ex n1 being Element of NAT st
for m1 being Element of NAT st m1 >= n1 holds
abs (((Partial_Sums (Maclaurin (sin,].(- r),r.[,x))) . m1) - (sin . x)) < p
then consider n being
Element of
NAT such that A5:
for
m being
Element of
NAT st
n <= m holds
abs (((Partial_Sums (x P_sin)) . m) - (sin . x)) < p
by A2, A3, SEQ_2:def 7;
set n1 =
(2 * n) + 2;
for
m1 being
Element of
NAT st
m1 >= (2 * n) + 2 holds
abs (((Partial_Sums (Maclaurin (sin,].(- r),r.[,x))) . m1) - (sin . x)) < p
proof
let m1 be
Element of
NAT ;
( m1 >= (2 * n) + 2 implies abs (((Partial_Sums (Maclaurin (sin,].(- r),r.[,x))) . m1) - (sin . x)) < p )
assume A6:
m1 >= (2 * n) + 2
;
abs (((Partial_Sums (Maclaurin (sin,].(- r),r.[,x))) . m1) - (sin . x)) < p
per cases
( m1 is even or not m1 is even )
;
suppose
m1 is
even
;
abs (((Partial_Sums (Maclaurin (sin,].(- r),r.[,x))) . m1) - (sin . x)) < pthen consider j being
Element of
NAT such that A7:
m1 = 2
* j
by ABIAN:def 2;
A8:
((n + 1) * 2) / 2
<= (j * 2) / 2
by A6, A7, XREAL_1:74;
then A9:
(n + 1) - 1
<= j - 1
by XREAL_1:11;
n + 1
>= 0 + 1
by XREAL_1:8;
then
j - 1 is
Element of
NAT
by A8, NAT_1:20;
then
abs (((Partial_Sums (x P_sin)) . (j - 1)) - (sin . x)) < p
by A5, A9;
hence
abs (((Partial_Sums (Maclaurin (sin,].(- r),r.[,x))) . m1) - (sin . x)) < p
by A1, A7, A8, Th26;
verum end; end;
end;
hence
ex
n1 being
Element of
NAT st
for
m1 being
Element of
NAT st
m1 >= n1 holds
abs (((Partial_Sums (Maclaurin (sin,].(- r),r.[,x))) . m1) - (sin . x)) < p
;
verum
end;
then
Partial_Sums (Maclaurin (sin,].(- r),r.[,x)) is convergent
by SEQ_2:def 6;
then A11:
lim (Partial_Sums (Maclaurin (sin,].(- r),r.[,x))) = sin . x
by A4, SEQ_2:def 7;
Sum (x P_cos) = cos . x
by SIN_COS:40;
then A12:
lim (Partial_Sums (x P_cos)) = cos . x
by SERIES_1:def 3;
set g = cos . x;
A13:
Partial_Sums (x P_cos) is convergent
by SIN_COS:39;
A14:
for p being real number st p > 0 holds
ex n1 being Element of NAT st
for m1 being Element of NAT st m1 >= n1 holds
abs (((Partial_Sums (Maclaurin (cos,].(- r),r.[,x))) . m1) - (cos . x)) < p
proof
let p be
real number ;
( p > 0 implies ex n1 being Element of NAT st
for m1 being Element of NAT st m1 >= n1 holds
abs (((Partial_Sums (Maclaurin (cos,].(- r),r.[,x))) . m1) - (cos . x)) < p )
assume
p > 0
;
ex n1 being Element of NAT st
for m1 being Element of NAT st m1 >= n1 holds
abs (((Partial_Sums (Maclaurin (cos,].(- r),r.[,x))) . m1) - (cos . x)) < p
then consider n being
Element of
NAT such that A15:
for
m being
Element of
NAT st
n <= m holds
abs (((Partial_Sums (x P_cos)) . m) - (cos . x)) < p
by A12, A13, SEQ_2:def 7;
set n1 =
(2 * n) + 1;
for
m1 being
Element of
NAT st
m1 >= (2 * n) + 1 holds
abs (((Partial_Sums (Maclaurin (cos,].(- r),r.[,x))) . m1) - (cos . x)) < p
hence
ex
n1 being
Element of
NAT st
for
m1 being
Element of
NAT st
m1 >= n1 holds
abs (((Partial_Sums (Maclaurin (cos,].(- r),r.[,x))) . m1) - (cos . x)) < p
;
verum
end;
then
Partial_Sums (Maclaurin (cos,].(- r),r.[,x)) is convergent
by SEQ_2:def 6;
then
lim (Partial_Sums (Maclaurin (cos,].(- r),r.[,x))) = cos . x
by A14, SEQ_2:def 7;
hence
( Partial_Sums (Maclaurin (sin,].(- r),r.[,x)) is convergent & sin . x = Sum (Maclaurin (sin,].(- r),r.[,x)) & Partial_Sums (Maclaurin (cos,].(- r),r.[,x)) is convergent & cos . x = Sum (Maclaurin (cos,].(- r),r.[,x)) )
by A4, A11, A14, SEQ_2:def 6, SERIES_1:def 3; verum