MathDB
JBMO Shortlist 2023 G2

Source: JBMO Shortlist 2023, G2

June 28, 2024
JBMO ShortlistgeometryAZE JBMO TST

Problem Statement

Let ABCABC be a triangle with AB<ACAB<AC and ω\omega be its circumcircle. The tangent line to ω\omega at AA intersects line BCBC at DD and let EE be a point on ω\omega such that BEBE is parallel to ADAD. DEDE intersects segment ABAB and ω\omega at FF and GG, respectively. The circumcircle of BGFBGF intersects BEBE at NN. The line NFNF intersects lines ADAD and EAEA at SS and TT, respectively. Prove that DGSTDGST is cyclic.