When a ray starts from x axis and rotates in anticlockwise direction and completes one round it covers 360 degree or 2 pi radian. in case the angle is more than 360 degree or 2 pi we just consider the angle between 0 and 360 degree or 0 and 2 pi. For example if we have 390 degree we consider 390 -360 = 30 degree only. Further we know that angle measured in clockwise direction is considered negative. Thus if we have angle 356 degree it is the same as -4 degree and 364 degree is the same as 4 degree.