Veblen, Oswald, 1880-1960, Young, John Wesley, 1879-1932 · Boston, New York [etc.] Ginn and Company · leaf 159
f Pa in theformula Px = Px + Pa is the group described in Example 2, p. 70. The sum oftwo points Pa and Pb might indeed have been defined as the point into whichPb is transformed when P0 is transformed into Pa by a projectivity of thisgroup. The associative law for addition would thus appear as a… … 49. Multiplication of points. Definition. In any plane through Ilet l0, lv lx be any three lines through P0, Pv P^ respectively, and let lxmeet l0 and lx in points A and B respectively (fig. 74). Let Px, Py be anytwo points of Z, and let the lines PXA and PyB meet l„ and l0 in the pointsX and Y…
Geometry, Projective
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