MathDB
locus of circumcenters, circles tangent to fixed line intersecting fixed circle

Source: 2011 XIV All-Ukrainian Tournament of Young Mathematicians, Qualifying p5

May 18, 2021
geometryLocusCircumcenterfixedUkrainian TYM

Problem Statement

The circle ω0\omega_0 touches the line at point A. Let RR be a given positive number. We consider various circles ω\omega of radius RR that touch a line \ell and have two different points in common with the circle ω0\omega_0. Let DD be the touchpoint of the circle ω0\omega_0 with the line \ell, and the points of intersection of the circles ω\omega and ω0\omega_0 are denoted by BB and CC (Assume that the distance from point BB to the line \ell is greater than the distance from point CC to this line). Find the locus of the centers of the circumscribed circles of all such triangles ABDABD.