MANUAL OF PLANE TRIGONOMETRY. BY THE REV. JOSEPH A. GALBRAITH, A. M., HODGES AND SMITH, GRAFTON-STREET, BOOKSELLERS TO THE UNIVERSITY. 1852. 183. C. 24. TRIGONOMETRY. INTRODUCTION. TRIGONOMETRY, as the name implies (rptywvov μETρEW), is that science which furnishes rules for the computation of triangles. As Geometry enables us to construct a triangle from three independent data, so Trigonometry enables us, from the same data expressed in numbers, to calculate its sides and angles. Triangles may be drawn either on a plane or spherical surface, and accordingly this branch of Mathematics is divided into Plane and Spherical Trigonometry. As a necessary preliminary to the investigation of trigonometrical rules, we proceed to explain the methods which are used for measuring angles, and expressing them by numbers. B |