Question 2.6.17: The points A′ and C′ are chosen on the diagonal BD of a para......

Mathematical Olympiads, Problems and Solutions from Around the World, 1996-1997 [1513040]

The points A′ and C′ are chosen on the diagonal BD of a parallelogram ABCD so that AA′ || CC′. The point K lies on the segment A′C, and the line AK meets CC′ at L. A line parallel to BC is drawn through K, and a line parallel to BD is drawn through C; these meet at M. Prove that D, M, L are collinear.

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