Here, the median coordinate at the moment t=0 seems to be A/2=0.02, but this value is not indicated in the topic setting conditions, but it looks like this.

1, we need to find the exact value on the diagram to find the initial phase of I, as shown in the figure below. According to the coordinate values of116 in the figure, the vibration is ahead of116× 4 π = π/4, so the initial phase is -π/4.

2. The initial phase can be set to φ0, so that the vibration equation can be written: x = 0.04cos (4π t+φ 0), and the coordinate value of this point (116,0.04) is substituted into the vibration equation, and 0.04 = 0.04cos (4π×/kloc-0).