| 释义 |
cissoid Math.|ˈsɪsɔɪd|
In 7 cissoeide.
[ad. Gr. κισσοειδ-ής ivy-like, f. κισσό-ς ivy: see -oid. The cusp of the cissoid resembles the re-entrant angles of an ivy-leaf.]
1. A curve of the second order invented by Diocles.
If from any two points lying on a fixed diameter of a circle, and equidistant from the centre, perpendiculars be drawn to the circumference, and a straight line be drawn from one extremity of the diameter to that of either perpendicular, the locus of the point in which this straight line cuts the other perpendicular will be a cissoid of Diocles, having its cusp at the end of the diameter. In later times the term has been extended to curves similarly described, where the generating curve is not a circle.
1656tr. Hobbes' Elem. Philos. (1839) 16. 1694 Halley Method finding Roots of Equations in Misc. Cur. (1708) II. 70 By the help of the Parabola, Cissoid, or any other Curve. 1798Loves of Triangles i. 11 in Anti-Jacobin 16 Apr., For me, ye Cissoids, round my temples bend Your wandering curves. 1879Salmon Higher Plane Curves V. 182 If a parabola roll on an equal one, the locus of the vertex of the moving parabola will be the cissoid.
2. cissoid angle.
1751Chambers Cycl. s.v. Angle, Cissoid Angle..is the inner angle made by two spherical convex lines intersecting each other. So1796Hutton Dict. Math. s.v. Angle.
Hence ciˈssoidal a., pertaining to a cissoid.
1796Hutton Math. Dict. s.v. Cissoid, The whole infinitely long cissoidal space, contained between the infinite asymptote..and the curves..of the cissoid, is equal to triple the generating circle. |