MathDB
similar triangles for juniors

Source: Czech-Polish-Slovak Match Junior 2019, individual p4 CPSJ

January 20, 2020
geometrysimilar triangles

Problem Statement

Let kk be a circle with diameter ABAB. A point CC is chosen inside the segment ABAB and a point DD is chosen on kk such that BCDBCD is an acute-angled triangle, with circumcentre denoted by OO. Let EE be the intersection of the circle kk and the line BOBO (different from BB). Show that the triangles BCDBCD and ECAECA are similar.