# The Product of the Circumradius and an Exradius

The Product of the Circumradius and an Exradius

Let ABC be a triangle with circumradius . Construct the excircle opposite A with excenter F and exradius . Let D and E be the intersections of the extensions of AB and AC with the excircle. Let G be the intersection of AF with the circumcircle of ABC. Then .

R

r

AF×GF=2Rr