Excerpt from Trigonometry: With the Theory and Use of Logarithms We have not striven for new methods, since those in common use are, in the main, good. At a few points, how ever, we think we have made improvements, as, for instance, in the proof of the formulas for the Sine and cosine of a: y where by using the conception Of projections, with which the student should have become thoroughly familiar at an earlier stage, the proof (in particular the figure) becomes very simple while remaining sufficiently concrete. We wish to thank Professors C. L. Bouton and E. V. Huntington Of Harvard University and Mr. Wm. A. Francis Of Phillips Exeter Academy who kindly read the manuscript and gave us the benefit Of valuable suggestions and criticism. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.