f(x) [p; p]
,
, 2p.
2l. 2l, , f(x) [l, l].
.
f(x) = 2p, [p; p]. ,
, (5)
(6)
""
(5) (6) :
, (7)
(8)
(7) (8) f(x) 2l [l;l].
, f(x) - . , .
) j(x) [l; l], . . j(-) = j().
.
:
x = - t Þ dx = - dt; :
.
) j(x) [l; l], . . j(-) = j().
= (, )
= .
, ,
. (9)
.
) .
f(x) [l, l].
, . , (9), :
(10)
, " ":
f(x) = f(x) Þ f(x) = .
) .
f(x) [ ; ], , ( ). , (10), :
(11)
" ":
f(x) = f(x) Þ f(x) = .
1. f(x) = |x| [p; p].
.
|x| , (10):
bn = 0, ,
. .
2. , :
.
f(x) , (11):
,
.
.., n bn = 0, n :
.
.
, , f(x) . , 0.