MathDB
Triangle is similar to two others

Source: SMO junior 2024 Q2

October 12, 2024
geometrysimilar trianglesparallelogram

Problem Statement

Let ABCDABCD be a parallelogram and points E,FE,F be on its exterior. If triangles BCFBCF and DECDEC are similar, i.e. BCFDEC\triangle BCF \sim \triangle DEC, prove that triangle AEFAEF is similar to these two triangles.