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In a bicentric quadrilateral ABCD, AB, BC, CD, and AD are tangent to the incircle at E, F, G, and H. Prove that EG and FH are perpendicular. A bicentric quadrilateral ABCD is a convex quadrilateral that has both an incircle I and a circumcircle O.

Home | Search | Geometry | Problems | All Problems | Open Problems | Visual Index | 10 Problems | Problems Art Gallery | Art | 901-910 | Quadrilaterals | Cyclic Quadrilateral | Tangential or circumscribed quadrilateral | Perpendicular lines | Solution / comment | by Antonio Gutierrez