IMO Shortlist 1990 problem 12
Kvaliteta:
Avg: 0,0Težina:
Avg: 0,0 Let
be a triangle, and let the angle bisectors of its angles
and
meet the sides
and
at the points
and
, respectively. The lines
and
meet the line through the point
parallel to
at the points
and
respectively, and we have
. Prove that
.
Original formulation:
Let
be a triangle and
the line through
parallel to the side
Let the internal bisector of the angle at
meet the side
at
and the line
at
and let the internal bisector of the angle at
meet the side
at
and the line
at
If
prove that















Original formulation:
Let
















Izvor: Međunarodna matematička olimpijada, shortlist 1990