Veblen, Oswald, 1880-1960, Young, John Wesley, 1879-1932 · Boston, New York [etc.] Ginn and Company · leaf 147
er P0 and axis P0Q changing P into P(Theorem 9, Chap. III). This elation (by the lemma above) changesA2 into another conic B2 through the points PQ and Q and tangentto p0. The lines through P0 are unchanged by the elation, whereastheir poles (on p0) are subjected to a parabolic projectivity.… … §47] PENCILS AND KANGES 133 That there is only one conic B2 through P satisfying the con-ditions of the theorem is to be seen as follows: Let QP meet p0 in S,and QP meet p0 in S (fig. 66). The points S and S must have thesame polar with regard to A2 and any conic B2, since this polarmust be the…
Geometry, Projective
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