Newcomb, Simon, 1835-1909 · New York, H. Holt and company · leaf 369
fifth point. Proof. Project the conic into a cir-cle. Let a, hy c and d be the projec-tions of the four fixed points, and Pthat of the fifth point. By a fundamental property of thecircle the angles aPh, hPc, etc., will re-main constant as P moves on the circle. Therefore the anharmonic ratio ofthe… … 340 MODERN OEOMETRT. lines pass from four fixed points on a conic to any fifth pointis called the anharmoiiic ratio of the four points of the conic.Def. The constant anharmonic ratio of the points in whichfour fixed tangents to a conic intersect a fifth tangent is calledthe anliarmo7iic ratio of…
Geometry, Analytic
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