MathDB
BC = DE - BE if <ADC =< DBA, A projection of A on BD , cyclic ABCD

Source: Switzerland - Swiss MO 2013 p3

July 16, 2020
geometryprojectionequal angles

Problem Statement

Let ABCDABCD be a cyclic quadrilateral with ∠ADC=∠DBA\angle ADC = \angle DBA. Furthermore, let EE be the projection of AA on BDBD. Show that BC=DE−BEBC = DE - BE .
Back to ProblemsView on AoPS