MathDB
Similarity appearing from nowhere

Source: All-Russian 2021/9.4

April 19, 2021
geometry

Problem Statement

Given an acute triangle ABCABC, point DD is chosen on the side ABAB and a point EE is chosen on the extension of BCBC beyond CC. It became known that the line through EE parallel to ABAB is tangent to the circumcircle of ADC\triangle ADC. Prove that one of the tangents from EE to the circumcircle of BCD\triangle BCD cuts the angle ABE\angle ABE in such a way that a triangle similar to ABC\triangle ABC is formed.