| 单词 | centre of involution |
| 释义 | > as lemmascentre of involution b. Geometry. A system of pairs of points on a right line, so situated that the product of the distances of the two points of each pair from a certain fixed point on the line (the centre of involution) is equal to a constant quantity. Hence in various extended uses (see quot. 1847). ΘΚΠ the world > relative properties > number > geometry > point > [noun] > sets or groups of points umbilic point1586 involution1847 triad1850 range1859 point group1887 tetrad1889 tristigm1889 neighbourhood1891 trinode1891 trigraphy1895 Cantor set1902 web1909 limit cycle1918 Leech lattice1968 1837 Chasles Aperçu Hist. 77 Desargues appelait la rélation qui constitue son beau théorème involution de six points.] 1847 Cayley in Cambr. & Dublin Math. Jrnl. II. 52 When three conics have the same points of intersection, any transversal intersects the system in six points, which are said to be in involution. It appears natural to apply the term to the conics themselves; and then it is easy to generalize the notion of involution so as to apply it to functions of any number of variables. 1879 G. Salmon Conic Sections (ed. 6) xvi. 311 The reciprocal of six points in involution is a pencil in involution. 1885 C. Leudesdorf tr. L. Cremona Elements Projective Geom. 101 In an involution the elements are conjugate to one another in pairs. < as lemmas |
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