TRIGONOMETRY

strictly speaking, deals with the measurement of triangles, plane or spherical; but it also includes the theory of the trigonometrical functions or ratios of an angle. Trigonometry, in its primary meaning, signifies the measurement of triangles, but now it has a wider scope, embracing all types of geometrical and algebraical investigations by means of certain quantities termed trigonometrical ratios. Trigonometry was originally a branch of astronomy, probably of Babylonian origin (Hipparch us, Menelaus). The Almagest of Ptolemy contains its first scientific exposition. In that work the circle is divided into 360 parts or degrees, each degree into sixty minutes, each minute into sixty seconds. The science had for object the measurement of a chord of a circle corresponding to a given angle, and Ptolemy made a table of these, obtained largely by the aid first used the expre ion sinus for the measurement of the half-ch ord—the | modern sine. The sine of the complementary angle is the cosine (Gunter). The tangent was the special creation of the Arabs, while the secant was introduced by the astronomer Copernicus (Cantor). Regiomontanus first made trigonometry a separate science, independent of astronomy. At present trigonometry is a conglomerate, which borrows from synthetic geometry, analytical geometry, and algebra. The construction of trigonometrical tables has of all times. ‘They are now usually incorporated in mathematical or logarithmic tables. (ancient. Trika), town, Greece; center of trade in wheat. Pop. 18,100.