all possible D for any choice of line l lie on a single circle.
Source: Tournament of Towns, Senior O- Level Paper, Spring 2020 , p5
June 4, 2020
geometrycirclesLocus
Problem Statement
Given are two circles which intersect at points and . Consider an arbitrary line through , let the second points of intersection of this line with the circles be and respectively. Let be the point of intersection of the tangents to the circles in those points. Let be the intersection of the line and the bisector of the angle . Prove that all possible for any choice of lie on a single circle.Alexey Zaslavsky