MathDB
Ratio between areas in a triangle divided by 3 lines

Source: Nordic MO 2009 Q1

April 20, 2013
ratiogeometrygeometry unsolved

Problem Statement

A point PP is chosen in an arbitrary triangle. Three lines are drawn through PP which are parallel to the sides of the triangle. The lines divide the triangle into three smaller triangles and three parallelograms. Let ff be the ratio between the total area of the three smaller triangles and the area of the given triangle. Prove that f13f\ge\frac{1}{3} and determine those points PP for which f=13f =\frac{1}{3} .