MathDB
<BAP =<CAQ wanted, <BAE = <CAF , EP//CD , FQ //CD

Source: 2010 Croatia MO (pre-TST) p3

August 5, 2020
geometryparallelequal angles

Problem Statement

Let DD be a point on the side ACAC of triangle ABCABC. Let EE and FF be points on the segments BDBD and BCBC respectively, such that BAE=CAF\angle BAE = \angle CAF. Let PP and QQ be points on the segments BCBC and BDBD respectively, such that EPCDEP \parallel CD and FQCDFQ \parallel CD. Prove that BAP=CAQ\angle BAP = \angle CAQ.