olymmath

USAJMO 2019 Problem 4

  • Day 2

Let ABCABC be a triangle with ∠ABC\angle ABC obtuse. The AA -excircle is a circle in the exterior of △ABC\triangle ABC that is tangent to side BCBC of the triangle and tangent to the extensions of the other two sides. Let EE , FF be the feet of the altitudes from BB and CC to lines ACAC and ABAB , respectively. Can line EFEF be tangent to the AA -excircle?

Proposed by Ankan Bhattacharya, Zack Chroman, and Anant Mudgal

Dataset text AI-MO AoPS. Quoted with source.

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