MathDB
Problem with a trapezium-proving two lines are parallel

Source:

July 17, 2012
geometrytrapezoid

Problem Statement

Let ABCDABCD be a trapezium with ABCDAB\parallel CD. Let PP be a point on ACAC such that CC is between AA and PP; and let X,YX, Y be the midpoints of AB,CDAB, CD respectively. Let PXPX intersect BCBC in NN and PYPY intersect ADAD in MM. Prove that MNABMN\parallel AB.