| 释义 |
subtense, n. Geom.|səbˈtɛns|
[ad. mod.L. subtensa (sc. linea line), fem. pa. pple. of subtendĕre to subtend. Cf. Sp., Pg. subtensa.]
a. A subtending line; esp. the chord of an arc. Also, the angle subtended by a line at a point.
1614Handson tr. Pitiscus' Trigonom. 31 A subtense is a right line, inscribed in a Circle, dividing the whole Circle into 2. Segments. 1656tr. Hobbes' Elem. Philos. (1839) 193 The subtenses of equal angles in different circles..are to one another as the arches which they subtend. 1678Cudworth Intell. Syst. i. iv. 653 Nor doth every one, who hath an Idea of a Rectangular Triangle, presently understand, that the Square of the Subtense, is Equal to the Squares of both the Sides. 1713Derham Phys. Theol. i. iv. (1727) 30 note, The whole Diameter of the Orb, viz. 20000, made the Subtense but of one Minute to one of the fix'd Stars. 1733Tull Horse-hoeing Husb. xxi. 305 Plow-Wrights always take this Subtense at the Fore-End of a Beam, whether it be a long Beam or a short one. 1803Phil. Trans. XCIII. 396 The total extent of the arch is about 15°, having half of its subtense on each side zero. 1958Engineering 21 Feb. 231/3 Fig. 4 shows the composite picture for the Horseshoe Falls, the angles signifying the angular subtense of any part of the Falls at the floodlights. 1974Nature 3 May 86/2 The test strips..had a subtense of between 1° and 2°. Ibid. 13 Dec. 535/2 Stereo blending does not work well when the angular subtense of the line joining the speakers exceeds about 60°.
b. attrib.: subtense method, a method of tacheometry in which the angle at the instrument is variable and the distance base is either constant or specially measured.
1897Geogr. Jrnl. (R.G.S.) X. 469 We..then made a traverse of the valley on the bar-subtense method. 1902Encycl. Brit. XXXIII. 143/2 Subtense method. 1905C. F. Close Topogr. & Geogr. Surv. 51 The general principle of subtense work and tacheometry is the measurement of the angle subtended at the observer by a short measured length at a distance. |