单项选择题
A.y=Acos(2πt/T-2πx/λ-1/2π) B.y=Acos(2πt/T+2πx/λ+1/2π) C.y=Acos(2πt/T+2πx/λ-1/2π) D.y=Acos(2πt/T-2πx/λ+1/2π)
A.f(x,t)=Acos(ax+bt) B.f(x,t)=Acos(ax-bt) C.f(x,t)=Acosax·cosbt D.f(x,t)=Asinax·sinbt
A.y=Acos[ω(t+L/u)+φ0] B.y=Acos[ω(t-L/u)+φ0] C.y=Acos[ωt+L/u+φ0] D.y=Acos[ωt-L/u+φ0]