Smart, Edward Howard · London : Macmillian and Co. · leaf 65
ither pair of the sides of thetriangle formed by the diagonalpoints of the quadrangle forms aharmonic pencil ivith the pair ofojyposite sides of the quadranglewhich meet at the same diagonalpoint. Either pair of the vertices of thetriangle formed by the diagonallines of the q^utdrilateral forms… … Let FG cut AB in H. Then, applying Cevas theorem to the triangle FAB, we haveFD.AH.BC= +DA.HB.CF. 38 PROJECTIVE GEOMETRY AH HB AE EB AH AE HB EB Also considering the transversal DCE cutting the sides ofthe same triangle, by Menelaus theorem FD.AE. BC= -DA. EB . CF. It follows that or .*. the range…
Geometry, Projective
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