JBMO-SL 2020 G3
Let be a right-angled triangle with and let be the foot of the perpendicular from on . Let be a point on the line with . Let (c) be the circumcircle of the triangle . Let be the second point of intersection of with and let be the antidiametric point of with respect to . Let be the point of intersection of the lines and . If the tangent to at meets at , prove that the points are concyclic.
Dataset text NuminaMath olympiads. Quoted with source.
Also JBMO 2020 Problem 2.
Solutions
No solution is on olymmath yet. Official and human solutions come first when they arrive. AI solutions come after them, with a label.