Veblen, Oswald, 1880-1960, Young, John Wesley, 1879-1932 · Boston, New York [etc.] Ginn and Company · leaf 237
on a conicall pass through the centerof the involution. Proof. Let ^M(fig. 90)be any conjugate pair (Anot a double point) of aninvolution of points on aconic C2. The line A A is then an invariant line of the collineation gener-ating the involution. Every line joining a pair of distinct… … Fig. 90 § 78] INVOLUTIONS 223 (Theorem 9, Cor. 3, Chap. III). It remains only to show that thecenter of this perspective collineation is the center of the involution.Let B, B (B not a double point) be any other conjugate pair of theinvolution, distinct from A, A. Then the lines AB and AB inter-sect…
Geometry, Projective
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