olymmath

ISL 2022 G1

    Let ABCDEA B C D E be a convex pentagon such that BC=DEB C=D E. Assume there is a point TT inside ABCDEA B C D E with TB=TD,TC=TET B=T D, T C=T E and ∠TBA=∠AET\angle T B A=\angle A E T. Let lines CDC D and CTC T intersect line ABA B at points PP and QQ, respectively, and let lines CDC D and DTD T intersect line AEA E at points RR and SS, respectively. Assume that points P,B,A,QP, B, A, Q and R,E,A,SR, E, A, S respectively, are collinear and occur on their lines in this order. Prove that the points P,S,Q,RP, S, Q, R are concyclic. (Slovakia)

    Official text Transcription from NuminaMath olympiads, checked word for word against the official paper. Quoted with source.

    Official text: IMO 2022 Shortlist booklet, page 8.

    Solutions

    Official solution Solution 1 by the IMO Problem Selection Committee

    The terms of the source let olymmath link to this solution but not copy it. Read the solution (IMO official site).

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