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IMO 2019 Problem 6

  • Day 2

Let II be the incentre of acute triangle ABCABC with AB≠ACAB\neq AC . The incircle ω\omega of ABCABC is tangent to sides BC,CABC, CA , and ABAB at D,E,D, E, and FF , respectively. The line through DD perpendicular to EFEF meets ω\omega at RR . Line ARAR meets ω\omega again at PP . The circumcircles of triangle PCEPCE and PBFPBF meet again at QQ .

Prove that lines DIDI and PQPQ meet on the line through AA perpendicular to AIAI .

Proposed by Anant Mudgal, India

Dataset text AI-MO AoPS. Quoted with source.

Official text: IMO 2019 official English paper, page 2.

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