Функциональные последовательности и ряды - 56 стр.

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x R cos x
x R
cos x = 1
x
2
2!
+
x
4
4!
x
6
6!
+. . .+(1)
n
x
2n
(2n)!
+. . . = 1+
X
n=1
(1)
n
x
2n
(2n)!
.
f(x) = sin x
sin x
x R sin x
(cos x)
0
= (1)
0
µ
x
2
2!
0
+
µ
x
4
4!
0
µ
x
6
6!
0
+ . . . +
µ
(1)
n
x
2n
(2n)!
0
+ . . . ,
sin x = x
x
3
3!
+
x
5
5!
x
7
7!
+ . . . +(1)
n1
x
2n1
(2n 1)!
+ . . . =
=
X
n=1
(1)
n1
x
2n1
(2n 1)!
,
x R
f(x) = ln (1 + x)
f
(n)
(x) = (1)
n1
(n 1)!
(1 + x)
n
, f(0) = 0, f
(n)
(0) = (1)
n1
(n 1)!,
ln (1 + x)
x
x
2
2
+
x
3
3
x
4
4
+ . . . + (1)
n1
x
n
n
+ . . . .
R = lim
n→∞
|a
n
|
|a
n+1
|
= lim
n→∞
n + 1
n
= 1.
(1, 1)
|x| > 1 x = 1
x = 1
(1, 1]
ln (1 + x)