Let t in I=Asin(ωx+φ) get the maximum and minimum values at the same time in any period of 1/50 seconds.

That is to say, there must be a maximum value and a minimum value within 1/50 seconds, so 1/50 is the period.

w = 2pi/T = 100 pi & gt； 3 14

So take 3 15.