MathDB
<ADB = < EDC iff MA = MC, ABCD with <A=<C=90^o given

Source: Dutch IMO TST1 2015 P1

August 5, 2019
right angleequal anglesequal segmentsgeometry

Problem Statement

In a quadrilateral ABCDABCD we have ∠A=∠C=90o\angle A = \angle C = 90^o. Let EE be a point in the interior of ABCDABCD. Let MM be the midpoint of BEBE. Prove that ∠ADB=∠EDC\angle ADB = \angle EDC if and only if ∣MA∣=∣MC∣|MA| = |MC|.
Back to ProblemsView on AoPS