PREFACE. THE purpose of the present treatise is to give a clear idea of Trigonometry, both Plane and Spherical, as a science, and also to explain its practical utility. The whole of the book is entirely original, and the examples have been written with a view to illustrate the principles of the science and their practical application, rather than to puzzle the student by an array of difficult formulæ. The series of tables at the end will, it is hoped, be found very useful. Linden Villa, Tottenham, N. W. ROSSITER. In any triangle the angles are usually expressed by A, B, and C, and the sides respectively opposite to these by a, b, and c. Sinx sin is usually written sin2, and so of all the other ratios. Angle (A + B) means an angle equal to the sum of the two angles A and B. If A = 40° and B = 35°, then A + B = 75°. Angle (AC) means the angle left when C is taken from A. If A = 40° and C = 35°, then A-C5°. |