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Quadrilateral-Similar-Triangles Collinearity Theorem

A proof is given in De Villiers, M. The Role of Proof in Investigative, Computer-based Geometry: Some personal reflections. Chapter in Schattschneider, D. & King, J. (1997). Geometry Turned On! Washington: MAA, pp. 15-24. For more info go to Geometry Turned On or buy the book on Amazon at Amazon: Geometry Turned On

My book "Some Adventures in Euclidean Geometry" also contains a proof, and is available as a PDF Download at Lulu. For more info go to Some Adventures in Euclidean Geometry

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