Veblen, Oswald, 1880-1960, Young, John Wesley, 1879-1932 · Boston, New York [etc.] Ginn and Company · leaf 61
e PXP^ D13 on the side Pl\, and Z>14 on the side PXP± (fig. 18).We observe first that the diagonal triangle is perspective with each of thefour triangles formed by a set of three of the vertices of the quadrangle,the center of perspectivity being in each case the fourth vertex. Thisgives rise to… … It may readily be verified, by selecting two perspective triangles,that the figure just formed is, indeed, a Desargues configuration. Thisspecial case of the Desargues configuration is called the quadrangle-quadrilateral configuration.^ EXERCISES 1. If p is the polar of P with regard to the…
Geometry, Projective
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