A SERIES OF MATHEMATICAL TEXTS EDITED BY EARLE RAYMOND HEDRICK THE CALCULUS By ELLERY WILLIAMS DAVIS and WILLIAM CHARLES ANALYTIC GEOMETRY AND ALGEBRA By ALEXANDER ZIWET and LOUIS ALLEN HOPKINS. By ALEXANDER ZIWET and LOUIS ALLEN HOPKINS. By ALFRED MONROE KENYON and LOUIS INGOLD. BRIEF TABLES WITH TRIGONOMETRY WITH By ALFRED MONROE KENYON and LOUIS INGOLD. By JOHN WESLEY YOUNG and FRANK MILLETT MORGAN. By ERNEST BROWN SKINNER. ELEMENTS OF PLANE TRIGONOMETRY WITH COM- By ALFRED MONROE KENYON and LOUIS INGOLD. ELEMENTS OF PLANE TRIGONOMETRY WITH BRIEF By ALFRED MONROE KENYON and LOUIS INGOLD. THE MACMILLAN TABLES Prepared under the direction of EARLE RAYMOND HEDRICK. By WALTER BURTON FORD and CHARLES AMMERMAN. By WALTER BURTON FORD and CHARLES AMMERMAN. By WALTER BURTON FORD and CHARLES AMMERMAN. CONSTRUCTIVE GEOMETRY Prepared under the direction of EARLE RAYMOND HEDRICK. JUNIOR HIGH SCHOOL MATHEMATICS By W. L. VOSBURGH and F. W. GENTLEMAN. This book is issued in a form identical with that of the books announced above PLANE TRIGONOMETRY BY ALFRED MONROE KENYON PROFESSOR OF MATHEMATICS, PURDUE UNIVERSITY AND LOUIS INGOLD ASSISTANT PROFESSOR OF MATHEMATICS THE UNIVERSITY OF MISSOURI New York THE MACMILLAN COMPANY 1921 K4 Astion. Dept. PREFACE The new THIS book carries out the chief motives which guided the authors in their larger work on Plane and Spherical Trigonometry. On the other hand it has been entirely rewritten, and has been made still more elementary in character. text forms a treatment of Plane Trigonometry which is quite brief, but which nevertheless deals with the most essential topics in more than the usual detail. This has been accomplished by omitting or curtailing certain topics that are seldom used by the student except in some special line of work. Thus all of Spherical Trigonometry and much of the detailed discussion of Trigonometric Identities and Equations is omitted. Such traditional topics as De Moivre's Theorem and infinite series were omitted from the author's larger work because they have few applications within the student's present grasp. These are of course omitted from the present book also. Thus this treatment contains a minimum of purely theoretical matter. Its entire organization is intended to give a clear view of the immediate usefulness of trigonometry. The solution of Triangles remains the principal motive. As such, this problem is attacked immediately and it is pushed to a definite conclusion early in the course. More complete outlines than usual have been given for the solution of oblique triangles by means of right triangles. This method of solution was emphasized recently in the Syllabus of the War Department for instruction in the S. A. T. C. A very brief course could well close with this method of solving triangles. Other practical problems are introduced to furnish a motive for the treatment of the general angle, the addition theorems, radian measure, etc. Among other applications, the composi V |