MathDB
EF // AB wanted, line tangent to (ABC)

Source: 2015 Latvia BW TST P5

December 16, 2022
geometryparallelcircumcircle

Problem Statement

BEBE is the altitude of acute triangle ABCABC. The line \ell touches the circumscribed circle of the triangle ABCABC at point BB. A perpendicular CFCF is drawn from CC on line \ell. Prove that the lines EFEF and ABAB are parallel.