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 IK^{2} + IJ^{2} = 2(R^{2} + d^{2}).
A bicentric quadrilateral ABCD is a convex quadrilateral that has both an incircle
I and a circumcircle O.
