""Elements of Plane Trigonometry"" is a mathematical textbook written by James Hann and first published in 1867. The book focuses on the study of trigonometry in two dimensions, specifically the relationships between angles and sides of triangles. The text covers topics such as the definitions of angles and trigonometric functions, the laws of sines and cosines, and the use of logarithms in trigonometric calculations. The book is intended for students...