[f. TRIGONOMETRY, on analogy of chronometer, thermometer: see -METER.] A name given to various trigonometrical instruments.
1767. J. Ferguson, Tables & Tracts (1771), 80. Mr. Mungo Murray … contrived a very useful instrument … which he calls The Armillary Trigonometer.
1796. Hutton, Math. Dict., Armillary Trigonometer, an instrument … consisting of five semicircles … so divided and graduated, as to serve for expeditiously resolving many problems in astronomy, dialling, and spherical trigonometry.
1828. Amer. Jrnl. Sc., XIV. 270. A trigonometer … which may be conveniently carried in the pocket.
1860. in Abridgm. Specif. Patents Optical, etc., Instr. (1875), 345. An improved mathematical or plotting instrument [denominated by the inventor] a protracting trigonometer.
