Let Γ\Gamma be a circle with centre II, and ABCDABCD a convex quadrilateral such that each of the segments ABAB, BCBC, CDCD and DADA is tangent to Γ\Gamma. Let Ω\Omega be the circumcircle of the triangle AICAIC. The extension of BABA beyond AA meets Ω\Omega at XX, and the extension of BCBC beyond CC meets Ω\Omega at ZZ. The extensions of ADAD and CDCD beyond DD meet Ω\Omega at YY and TT, respectively. Prove that AD+DT+TX+XA=CD+DY+YZ+ZC.AD + DT + TX + XA = CD + DY + YZ + ZC.