MathDB
AD = AO wanted, 2 circles and angle bisector related

Source: Switzerland - Swiss ΜΟ 2017 p1

July 14, 2020
geometryangle bisectorcirclesequal segments

Problem Statement

Let AA and BB be points on the circle kk with center OO, so that AB>AOAB> AO. Let CC be the intersection of the bisectors of OAB\angle OAB and kk, different from AA. Let DD be the intersection of the straight line ABAB with the circumcircle of the triangle OBCOBC, different from BB. Show that AD=AOAD = AO .