MathDB

Jbmo problem 3

Source:

June 26, 2015

geometry

Problem Statement

Let

ABC

be an acute triangle.The lines

M

and

l_2

are perpendicular to

AB

at the points

A

and

B

, respectively.The perpendicular lines from the midpoint

M

of

AB

to the lines

AC

and

BC

intersect

l_1

and

l_2

at the points

E

and

F

, respectively.If

D

is the intersection point of the lines

EF

and

MC

, prove that

\angle ADB = \angle EMF.

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