• 2021-04-14
    【多选题】若f 1 (t) = ɛ (-t) , f 2 (t) = e t ,则f 1 (t)* f 2 (t) =
    A. f 1 ꞌ (t)* f 2 (–1) (t) B. f 1 (–1) (t)* f 2 ꞌ (t) C. f 1 (t-3)* f 2 (t+3) D. f 1 (–3) (t)* f 2 ꞌꞌꞌ (t)
  • f 1 (–1) (t)* f 2 ꞌ (t);
    f 1 (t-3)* f 2 (t+3); f 1 (–3) (t)* f 2 ꞌꞌꞌ (t)

    内容

    • 0

      设f()1()(t)和f()2()(t)都是周期信号,其基波周期分别为T()1()和T()2(),如果和式f()1()(t)+f()2()(t)是周期的,它的基波周期是()A.()T()1()的周期()B.()T()2()的周期()C.()T()1()和T()2()的最小公倍数

    • 1

      在交流电路中,频率f/和周期T的关系式是()。 A: T=2πf; B: T=2π/ωt; C: T=f; D: T=1/f。

    • 2

      【单选题】已知f 1 (t)=tε(t),f 2 (t)=ε(t)-ε(t-2)试求y(t)=f 1 (t)*f 2 (t-1)*δ’(t-2) A. (t-3)u(t-3)-(t-5)u(t-5) B. (t-2)u(t-2)-(t-5)u(t-5) C. (t-3)u(t-3)-(t-4)u(t-4) D. (t-3)u(t-2)-(t-5)u(t-3)

    • 3

      设参数方程,确定了y是x的函数,f″(t)存在且不为零,则d2y/d2x的值是:() A: -1/f″(t) B: 1/[f″(t)]2 C: -1/[f″(t)]2 D: 1/f″(t)

    • 4

      交流电周期、频率、角频率关系正确的是() A: T=1/f B: f=1/T C: ω=2π/T D: ω=2πf