whenever the things contained by the sin function = a factor of 2pi , a complete cycle is made. so in this case, whenever 2pi/7x = 2pi , a complete cycle is made. 2pi/7x = 2pi 1/7x = 2pi/2pi 1/7x = 1 7x = 1 x = 1/7 therefore, the period is x = 1/7 for every cycle
