A quadrilateral of any shape whatever is divided by a transversal into two quadrilaterals. The diagonals of the original figure and those of the two resulting (smaller) figures are then drawn. Show that their three points of intersection are collinear. ([i]American Mathematical Monthly[/i] [Vol. 22, No. 5 (May 1915),pp. 165-166]
(solved by Anna Margaret Mullikin (March 7, 1893 - August 24, 1975)
