MathDB
SMO 2014

Source:

May 22, 2015
geometrygeometry proposed

Problem Statement

In a triangle ABCABC, let DD and EE be the feet of the angle bisectors of angles AA and BB, respectively. A rhombus is inscribed into the quadrilateral AEDBAEDB (all vertices of the rhombus lie on different sides of AEDBAEDB). Let φ\varphi be the non-obtuse angle of the rhombus. Prove that φmax{BAC,ABC}\varphi \le \max \{ \angle BAC, \angle ABC \}
Proposed by Dusan Djukic IMO Shortlist 2013IMO \ Shortlist \ 2013