Problem A. 461. (October 2008)
A. 461. The exsphere of the tetrahedron ABCD, corresponding to face ABC, touches the face ABC at P. The exsphere, corresponding to face ABD, touches ABD at Q. Show that .
Deadline expired on November 17, 2008.
6 students sent a solution. 5 points: Éles András, Nagy 235 János, Tomon István, Wolosz János. 4 points: Nagy 314 Dániel. 0 point: 1 student.