Problem B. 4670. (December 2014)

B. 4670. Let \(\displaystyle A_1\), \(\displaystyle B_1\) and \(\displaystyle C_1\) be the midpoints of the sides of a triangle \(\displaystyle ABC\). Drop a perpendicular from \(\displaystyle A_1\) to the angle bisector drawn from vertex \(\displaystyle A\), from \(\displaystyle B_1\) to the angle bisector drawn from vertex \(\displaystyle B\), and from \(\displaystyle C_1\) to the angle bisector drawn from vertex \(\displaystyle C\). Let \(\displaystyle A_2\) denote the intersection of the perpendiculars from \(\displaystyle B_1\) and from \(\displaystyle C_1\). The points \(\displaystyle B_2\) and \(\displaystyle C_2\) are obtained in a similar way. Show that the lines \(\displaystyle A_1A_2\), \(\displaystyle B_1B_2\) and \(\displaystyle C_1C_2\) are concurrent.

Suggested by Zs. Sárosdi, Veresegyház

(3 pont)

Deadline expired on January 12, 2015.

Statistics:

36 students sent a solution.
3 points:	Csépai András, Gál Boglárka, Geng Máté, Gyulai-Nagy Szuzina, Heinc Emília, Juhász 326 Dániel, Kerekes Anna, Khayouti Sára, Nagy Dávid Paszkál, Németh 123 Balázs, Polgár Márton, Vankó Miléna, Várkonyi Dorka, Williams Kada.
2 points:	Andó Angelika, Ratkovics Gábor, Sal Kristóf, Szakály Marcell, Szász Dániel Soma.
1 point:	8 students.
0 point:	9 students.

Problems in Mathematics of KöMaL, December 2014