In a bicentric quadrilateral ABCD, I
is the incenter, O the circumcenter, R the circumradius, and IO
= d. BI
and DI extended meet the circumcircle O at J and K,
respectively. Prove that IK2 + IJ2 = 2(R2 + d2).
A bicentric quadrilateral ABCD is a convex quadrilateral that has both an incircle
I and a circumcircle O.