Let ABCD be a quadrilateral inscribed in a circle Ω. Let the tangent to Ω at D meet rays BA and BC at E and F, respectively. A point T is chosen inside △ABC so that TE∥CD and TF∥AD. Let K=D be a point on segment DF satisfying TD=TK. Prove that lines AC,DT, and BK are concurrent. ISL 2021IMO Shortlistgeometrycyclic quadrilateralconcurrency