| Problem 3. Let  be an acute scalene triangle with circumcenter  . Let  be the foot of the altitude from  to the side  . The lines  and  intersect at  . Let  be the line through  perpendicular to  . The line  intersects  and  at  and  , respectively. Denote by  the circumcircle of triangle  . Line  intersects  again at  . Prove that
  and the circumcircles of triangles  and  have a common point. proposed by Bosnia and Herzegovina   |