ion of the opposite angles of theordinaiy quadrilateral. The thi-ee straight lines joining opposite verticesare called diagonal lines, or diagonals. The tri-angle formed by these diagonal lines is called thediagonal triangle of the complete quadrilateral. Thns AC, BD, EF are the diagonals; and PQR… … Consider tlie triangle EAF. Then since EB, AQ, FDpass through the point C, therefore ED.AB.FQ^.^ ^rpj^^ ^j ^^^^^DA . BF . QEAlso since DBR cuts the sides of the triangle EAF,therefore ED. AB.FR^-^ .rpi^^^ ^f Menelaus.)DA . BF . RE Hence =^ = —, and R, F, QyEform, a harmonic range.QE RE Therefore…
Geometry · Geometry, Plane
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![An illustration from Brief synopsis of the course of lectures in descriptive geometry; as arranged for the first year Faculty of Applied Science and Engineering, University of Toronto. [By] J. Roy Cockburn (1922)](https://img.insideoutlibrary.com/img/200/ia-fybriefsynopsiso00cockuoft-25-22.webp)
