IMO Shortlist 2006 problem C2
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Let
be a regular
-gon. A diagonal is called good if its endpoints divide the boundary of
into two parts, each composed of an odd number of sides of
. The sides of
are also called good.
Suppose
has been dissected into triangles by
diagonals, no two of which have a common point in the interior of
. Find the maximum number of isosceles triangles having two good sides that could appear in such a configuration.





Suppose



Izvor: Međunarodna matematička olimpijada, shortlist 2006