The point here is that the two ω have different meanings. Ω 0 in the vibration equation x = acos (Ω 0t+α) is the angular frequency of simple harmonic vibration, and its relationship with the period is: Ω 0 = 2π/t, which is obviously a constant in the process of vibration, while dφ/dt=ω is the angular velocity in the process of vibration, and the different positions in the process of vibration are different. Dφ/dt=ω=0。 In order to avoid confusion between the angular velocity at t=0 expressed by ω0 and the angular frequency ω0 of the last vibration, the author uses v0 to express the velocity at 0.