MathDB

Find an angle

Source: Baltic Way 2016, Problem 18

November 5, 2016

geometry

Problem Statement

Let

ABCD

be a parallelogram such that

\angle BAD = 60^{\circ}.

Let

K

and

L

be the midpoints of

BC

and

CD,

respectively. Assuming that

ABKL

is a cyclic quadrilateral, find

\angle ABD.

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