| 释义 |
pentagonal, a. (n.)|pɛnˈtægənəl|
[f. prec. + -al1: cf. F. pentagonal (1533 in Hatz.-Darm.).]
1. Geom., etc. Of or pertaining to a pentagon; of the form of a pentagon, having five angles and five sides, five-cornered or five-sided.
Pentagonal figure in quot. 1612 = pentagonon 1.
1571Digges Pantom. ii. ix. M iv b, The Area of this pentagonall superficies. 1612Selden Illustr. Drayton's Poly-olb. ix. 154 The supposed..Druttenfuss, i. a Pentagonall figure, ingrauen with Ὑγιεια or Ὑγεια,..in Germany they reckon it for a preseruatiue against Hobgoblins. 1785Martyn Rousseau's Bot. xvi. (1794) 172 The species is distinguished by its pentagonal calyx. 1872Nicholson Palæont. 110 Order 11. Asteroidea,..the body is star-shaped or pentagonal, and consists of a central ‘disc’, surrounded by five or more lobes or ‘arms’. 1879Cassell's Techn. Educ. IV. 136/1 The Italian engineers..adopted the pentagonal or bastion shape.
b. Applied to a solid figure or body of which the base or section is a pentagon; having five edges or dihedral angles.
1570Billingsley Euclid xi. Def. x. 314 If the base be a Pentagon, then is it a Pentagonall or fiueangled Pyramis. 1771Pennant Tour Scot. in 1769 (1790) 68 Great columns of stone..regularly pentagonal or hexagonal. 1840Lardner Geom. 232 A regular pentagonal pyramid.
c. Contained by pentagons, as a solid figure.
1851Richardson Geol. v. (1855) 91 The pentagonal dodecahedron may likewise be formed on the cube. 1895Story-Maskelyne Crystallogr. §177 The pentagonal icositetrahedron (or twenty-four-pentagonohedron).
2. Arith. pentagonal numbers: the series of polygonal numbers 1, 5, 12, 22, 35, 51, 70, 92, etc. formed by continuous summation of the arithmetical series 1, 4, 7, 10, 13, 16, etc.
1670Collins in Rigaud Corr. Sci. Men (1841) II. 196 It is likewise a pentagonal number, or composed of two, three, four, or five pentagonal numbers. 1795Hutton Math. Dict., Figurate Numbers, such as do or may represent some geometrical figure,..as triangular, pentagonal, pyramidal, etc., numbers.
b. as n. A pentagonal number.
1795Hutton Math. Dict. s.v. Polygonal Numbers, The Angles, or Numbers of Angles, are the same as those of the figure... So the angles..of the pentagonals are 5, of the hexagonals 6, and so on. Ibid., Formulæ for the sums of n terms of the several ranks of Polygonal numbers... Pentagonals, 3n2 + 3n + 0 / 6 n.
Hence penˈtagonally adv., in a pentagonal form; so † penˈtagonary, † pentaˈgo nian adjs. = pentagonal; pentagonoˈhedron [after rhombohedron, etc.], a solid figure contained by pentagons; penˈtagonoid a., resembling a pentagon, somewhat pentagonal.
1658Sir T. Browne Gard. Cyrus iii, The flowers before explication are *pentagonally wrapped up with some resemblance of the blatta or moth.
1658R. White tr. Digby's Powd. Symp. (1660) 72 The *pentagonary figure of every one of those stones.
1598R. Haydocke tr. Lomazzo i. 111 Their circular, *pentagonian, hexagonian, octagonian, square and crosse ones.
1895Story-Maskelyne Crystallogr. §183 The pentagon-dodecahedron... The twelve-*pentagonohedron is a very characteristic form of certain mineral species.
1882Sladen in Jrnl. Linn. Soc. XVI. 203 Marginal contour *pentagonoid. |