| 释义 |
conchoid, n. and a.|ˈkɒŋkɔɪd|
[ad. Gr. κογχοειδής mussel-like, f. κόγχη mussel-shell + -ειδης -form: see -oid: in mod.F. conchoïde.]
A. n. Geom. A plane curve of the fourth order invented by Nicomedes.
If from a fixed point (the pole) straight lines be drawn intersecting a fixed straight line (the asymptote), and on these lines points be taken at a constant distance from their intersections with the asymptote, this succession of points will form a conchoid of Nicomedes consisting of two branches, one on each side of the asymptote.
1798Frere & Canning Loves of Triangles 12 in Anti-Jacobin 16 Apr. (1852) 106 Ye Conchoids extend. 1807Hutton Course Math. II. 320 To find the point of inflexion in the Conchoid of Nicomedes. 1821Coleridge in Blackw. Mag. X. 255, I never take a turn round the garden without thinking of his billow-lines and shell-lines, under the well-sounding names of Cumaïds and Conchoïds. 1879G. Salmon Higher Plane Curves ii. 44 A curve, called the conchoid of Nicomedes, invented by that geometer for the solution of the problem of finding two mean proportionals.
b. spherical conchoid: Herschel's name for a similar curve, traced on the surface of a sphere.
1797Encycl. Brit. II. 483/1.
B. adj. = conchoidal.
1802Howard in Phil. Trans. XCII. 207 Its fracture is usually conchoid. |