circumcenter of BLD lies on circumcircle of trapezoid ABCD
Source: 2022 Oral Moscow Geometry Olympiad grades 8-9 p1
April 17, 2022
geometrytrapezoidcircumcircleConcyclic
Problem Statement
Given an isosceles trapezoid . The bisector of angle intersects the base at point . Prove that the center of the circle circumscribed around triangle lies on the circle circumscribed around the trapezoid.(Yu. Blinkov)