• 2022-05-30
    设[img=101x68]17da617d02ef0f0.png[/img],当t =( )时,R(A) = 2。
    A: -2
    B: 2
    C: 4
    D: -4
  • D
    本题目来自[网课答案]本页地址:https://www.wkda.cn/ask/tjzmeemtezzzooo.html

    内容

    • 0

      ‏信号f(t)=[img=37x22]180306afbecf53b.png[/img]则f(t)的傅里叶变换为( )。​ A: 4πδ(ω-2) B: 4πδ(ω+2) C: 4δ(ω-2) D: 4δ(ω+2)

    • 1

      设随机变量(X,Y)在区域{(x,y): 0<|y|< x <2}内均匀分布,则以下结果正确的是 A: 当0<x<2时,[img=96x25]1802dded7db6eef.png[/img]. B: E(X)=4/3 C: 当0<|y|<2时,[img=105x45]1802dded872b92f.png[/img]. D: P(X<1)=0.5 E: 当0<x<2时,[img=110x45]1802dded915de6e.png[/img]. F: E(X)=2/3 G: 当0<y<2时,[img=95x43]1802dded9a54300.png[/img].

    • 2

      求微分方程[img=143x21]17da5f14490e50e.png[/img]的通解,实验命令为(). A: dsolve(D2y-2*Dy+5*y=sin(2*x),x)ans =exp(x)*sin(2*x)*C2+exp(x)*cos(2*x)*C1+1/17*sin(2*x)+4/17*cos(2*x) B: dsolve('D2y-2*Dy+5*y=sin(2*x)','x')ans =cos(2*x)*(sin(4*x)/17 - cos(4*x)/68 + 1/4) - sin(2*x)*(cos(4*x)/17 + sin(4*x)/68) + C1*cos(2*x)*exp(x) - C2*sin(2*x)*exp(x) C: dsolve(D2y-2*Dy+5*y=sin(2*x),'x','y')ans =exp(x)*sin(2*x)*C2+exp(x)*cos(2*x)*C1+1/17*sin(2*x)+4/17*cos(2*x)

    • 3

      设[img=100x29]17de70c8070cc27.png[/img],则[img=215x29]17de70c8288ec52.png[/img] A: 4 B: 0 C: 2 D: -2

    • 4

      设[img=84x42]17e439d09bcb7c0.png[/img],则[img=52x22]17e439d0af936fb.png[/img] A: 2 B: -2 C: 0 D: -4