OF PLANE AND SPHERICAL TRIGONOMETRY, WITH THEIR APPLICATIONS TO MENSURATION, SURVEYING, AND NAVIGATION. BY ELIAS LOOMIS, LL. D., PROFESSOR OF NATURAL PHILOSOPHY AND ASTRONOMY IN YALE COLLEGE, REVISED EDITION. NEW YORK: HARPER & BROTHERS, FRANKLIN SQUARE. 1890. 128 pp., 90 cents. 219 pp., $1 00. Key to Treatise on Algebra, for Use of Teachers. ELEMENTS OF GEOMETRY. Revised Edition. 388 pp., $1 00. ELEMENTS OF TRIGONOMETRY, SURVEYING, AND NAVIGATION. Revised Edition. 194 pp., $1 00. The Trigonometry and Tables, bound in one volume. 360 pp., $1 50. ELEMENTS OF ANALYTICAL GEOMETRY. Revised Edition. 261 pp., $1 00. PRACTICAL ASTRONOMY. 499 pp., $1 50. TREATISE ON ASTRONOMY. 351 pp., $1 50. TREATISE ON METEOROLOGY. 308 pp., $1 50. PUBLISHED BY HARPER & BROTHERS, NEW York. Any of the above works sent by mail, postage prepaid, to any part of the Entered, according to Act of Congress, in the year one thousand eight hundred and fifty-eight, by HARPER & BROTHERS, In the Clerk's Office of the District Court of the Southern District of New York. Copyright, 1886, by HARPER & BROTHERS. PREFACE. THE stereotype plates of my "Elements of Trigonometry" having become so much worn in the printing of more than 60,000 copies that they were no longer fit for use, it became necessary to recast them, and I have improved the opportunity to make a thorough revision of the work. At the same time I have introduced a radical change which I have had in contemplation for several years. In the former editions, in conformity with the usage of the old English mathematicians, the trigonometrical functions were regarded as lines; in this revised edition they are regarded as ratios, in conformity with a usage which has now become well-nigh universal. I am of the opinion that the old system has some important advantages in the training of students who have no decided aptitude for mathematical studies; but since the weight of authority is decidedly against this system, I have decided to abandon it. It is hoped that the changes made in this revised edition may receive the general approval of teachers. |