MathDB
Easy similarity in parallelogram

Source: VII Caucasus Mathematical Olympiad

March 13, 2022
geometryparallelogramnumber theory

Problem Statement

In parallelogram ABCDABCD, points EE and FF on segments ADAD and CDCD are such that BCE=BAF\angle BCE=\angle BAF. Points KK and LL on segments ADAD and CDCD are such that AK=EDAK=ED and CL=FDCL=FD. Prove that BKD=BLD\angle BKD=\angle BLD.