Transversala nu este paralela cu o latură a triunghiului

Sorry, the GeoGebra Applet could not be started. Please make sure that Java 1.4.2 (or later) is installed and active in your browser ()[br][br]Ken Frank, Created with GeoGebra[br] [br][br][br][br][br]Drag points H and D to show various positions of the non-parallel transversal HF.[br][br]Point H is on side CB extended, while points D and F are either both interior or both exterior to the triangle.[br][br]You can think of 'walking' the sides of triangle ABC to construct the Menelaus equation. Start at any vertex of triangle ABC, such as point B. Go from B to D, D to A, A to F, F to C, C to H, and H back to B. Write the ratios as you walk. Between the letters of any two triangle vertices comes the letter of the transversal's intersection point for that side.[br][br]Do you see that it is equally true that AB is a transversal of triangle HFC? Menelaus can be written for triangle HFC as[br](FD/DH) (HB/BC) (CA/AF) = 1[br][br]The Menelaus Theorem can be proved using similar triangles, as in the next diagram.