A.36N·s
B.90N·s
C.64N·s
D.81N·s
[单选题]A.1B.2C.4D.1/4
[单选题]A.xyB.2xyC.D.xy+1
[单选题]A.B.C.D.
[单选题]A.振幅为1,初相为πB.振幅为7,初相为4/3πC.振幅为7,初相为7/6πD.振幅为1,初相为1/6π