MEMO 2017 ekipno problem 5


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12. rujna 2018.
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Let ABC be an acute-angled triangle with AB > AC and circumcircle \Gamma. Let M be the midpoint of the shorter arc BC of \Gamma, and let D be the intersection of the rays AC and BM. Let E \neq C be the intersection of the internal bisector of the angle ACB and the circumcircle of the triangle BDC. Let us assume that E is inside the triangle ABC and there is an intersection N of the line DE and the circle \Gamma such that E is the midpoint of the segment DN.
Show that N is the midpoint of the segment I_B I_C, where I_B and I_C are the excentres of ABC opposite to B and C, respectively.

Izvor: Srednjoeuropska matematička olimpijada 2017, ekipno natjecanje, problem 5