![](https://csdnimg.cn/release/download_crawler_static/85875330/bg1.jpg)
4.4 解:
(a)
4cos1)()4()4()(2)(
11
txjX ,
(b)
t
t
t
tjtj
jtdjdtjtjXdejXtx
2
sin4
)2cos1(2
2
0
1
2
1
2
1
2
sin2)sin)(cos()()(
4.21 解:
(a)
0),(cos)(
0
atutetx
at
ja
FT
at
tue
1
)(
;
)()(cos
000
FT
t
2
0
2
00
][)]()([)(
)(
1
)(
1
2
1
00
1
2
1
ja
ja
jajaja
jX
(h) 设
)(
1
tx
如图所示:
则
2
11
1
)(
T
k
FS
atx
;
kk
T
k
FT
kkajXtx )()(2)()(
2
11
而
)1()(2)(
11
txtxtx
k
k
k
jj
kkeejXjXjX )(])1(2[)()2()()(2)(
11
4.22 解:
t
0
-2-4