The radius of the circle r = (AF 2+AE 2) (1/2)

The included angle between OA and positive semi-axis of Y axis A = Arctan (AF/AE) < 0.

The angle between OB and the positive semi-axis of y axis b = angle AOB+a.

OB (UK, Belgium)

BG=Rsinb

BH=Rcosb

This formula can satisfy the numerical value (including positive and negative) of any point B on the circle.