MathDB
May Olympiad 2012, Level 2, Problem 3

Source:

August 25, 2014
geometryperpendicular bisectorangle bisector

Problem Statement

Let ABCABC be a triangle such that ABC=2BCA\angle{ABC} = 2\angle{BCA} and CAB>90\angle{CAB}>90^\circ. Let MM be the midpoint of BCBC. The line perpendicular to ACAC that passes through CC cuts the line ABAB at point DD. Show that AMB=DMC\angle{AMB} = \angle{DMC}.