Geom. [ad. mod.L. subtensa (sc. linea line), fem. pa. pple. of subtendĕre to SUBTEND. Cf. Sp., Pg. subtensa.] A subtending line; esp. the chord of an arc.
1614. Handson, trans. Pitiscus’ Trigonom., 31. A subtense is a right line, inscribed in a Circle, dividing the whole Circle into 2. Segments.
1656. trans. Hobbes’ Elem. Philos. (1839), 193. The subtenses of equal angles in different circles … are to one another as the arches which they subtend.
1678. Cudworth, 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.
1713. Derham, 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.
1733. Tull, 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.
1803. Phil. Trans., XCIII. 396. The total extent of the arch is about 15°, having half of its subtense on each side zero.
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.
1897. Geogr. Jrnl. (R.G.S.), X. 469. We … then made a traverse of the valley on the bar-subtense method.
1902. Encycl. Brit., XXXIII. 143/2. Subtense method.
1905. C. F. Close, Topogr. & Geogr. Surv., 5. 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.
