MEMO 2014 ekipno problem 6
Dodao/la:
arhiva24. rujna 2014. Let the incircle
of the triangle
touch its side
at
. Let the line
intersect
at
and denote the excentre of
opposite to
by
. Let
and
be the midpoints of
and
respectively.
Prove that the points
,
,
, and
are concyclic.
%V0
Let the incircle $k$ of the triangle $ABC$ touch its side $BC$ at $D$. Let the line $AD$ intersect $k$ at $L \neq D$ and denote the excentre of $ABC$ opposite to $A$ by $K$. Let $M$ and $N$ be the midpoints of $BC$ and $KM$ respectively.
Prove that the points $B$, $C$, $N$, and $L$ are concyclic.
Izvor: Srednjoeuropska matematička olimpijada 2014, ekipno natjecanje, problem 6