TWENTIETH CENTURY TEXT-BOOKS THE YOUNG AND JACKSON ALGEBRA SERIES A High School Algebra x, 508 pages, $1.15. A High School Algebra, Part I vii, 294 pages, 95 cents. A High School Algebra, Part II viii, 216 pages, 70 cents. Elementary Algebra xii, 442 pages, $1.12. A First Course in Elementary Algebra ix, 294 pages, 95 cents. A Second Course in Elementary Algebra vii, 206 pages, 70 cents. All of the above texts may be had with or without answers. APPLETON AND COMPANY D. NEW YORK 163 CHICAGO PLANE GEOMETRY BY J. W. A. YOUNG, PH.D. ASSOCIATE PROFESSOR OF THE PEDAGOGY OF MATHEMATICS PREFACE THE facts of geometry are unchangeable. The experience of the past has determined what body of these facts is suitable for secondary school work, both for teaching the geometric type of reasoning and for application in the arts and sciences. Therefore, a book that would avoid the bizarre and the erratic must profit by the experience of the past and confine its attempt at novelty to the field of method. More skillful presentations and more effectual ways of reaching the chief ends of the teaching of geometry are always possible. Accordingly, the authors of this work have given full consideration to the history of geometry and to the views of professional committees of recent date, and they here present in the form of definitions, propositions, and corollaries, that minimum of essentials which has become standard. Furthermore, every effort has been made by means of phraseology, sequence, and typographic arrangement, to secure the maximum of lucidity. The time is past when it was necessary to argue that in studying geometry the pupil should not merely learn demonstrations but also do some demonstrating himself. Accordingly, frequent and extensive sets of exercises furnish much occasion for actual demonstration on the part of the pupil. But the demonstrations of the basic theorems have been given in full or in sufficiently detailed outline, both in order that the pupil may throughout the subject have authoritative models for his guidance, and also that the building up of the main body of the subject should not be left to the hazards of the V |