MathDB
computational with tangent circles

Source: (2021-) 2022 XV 15th Dürer Math Competition Finals Day 2 E+13

December 12, 2022
tangent circlesgeometry

Problem Statement

Circle k1k_1 has radius 1010, externally touching circle k2k_2 with radius 1818. Circle k3k_3 touches both circles, as well as the line ee determined by their centres. Let k4k_4 be the circle touching k2k_2 and k3k_3 externally (other than k1k_1) whose center lies on line ee. What is the radius of k4k_4?