평면기하학 plane geometry 平面幾何學 .The Book of Plane Geometry, by George Albert Wentworth
평면기하학 plane geometry 平面幾何學 을 설명하면 평면에서 도형의 모양 ·크기 ·위치관계 등등을 공부하는 기하학의 하나의 분야로 초등기하학이란 것은 모두 여기에 포함됨.
그리스의 수학자인 유클리드의 기하학원본을 보면 제6권까지 평면 기하학을 포함하고 중대한 부분을 모두 포함. 평면 기하학의 대상이 되는 도형을 평면도형 이라고 함, 보기를 들면 이책의 목차및 본문의 내용처럼 평면상의 어떤 직선도형 ·원 ·이차곡선 등이 여기에 포함. 즉 이책의 내용처럼 먼저 기하학의 기초 용어를 정리하고서 다음으로 , 렉타앵글 정사각형, 폴리곤 즉 다각형 그리고 삼각형인 트라이 앵글 , 서클인 원 즉 원형 도형을 그림과 예문과 보기 문제등으로 설명함.
초 중 고교 수학 그리고 나아가서 대학의 기초수학에 중요한 책.

평면기하학 plane geometry 平面幾何學 .The Book of Plane Geometry, by George Albert Wentworth
Contents
GEOMETRY. 1
INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . . . . 1
GENERAL TERMS. . . . . . . . . . . . . . . . . . . . . . . . 3
GENERAL AXIOMS. . . . . . . . . . . . . . . . . . . . . . . 6
SYMBOLS AND ABBREVIATIONS. . . . . . . . . . . . . . . 6
PLANE GEOMETRY. 7
BOOK I. RECTILINEAR FIGURES. 7
DEFINITIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . 7
THE STRAIGHT LINE. . . . . . . . . . . . . . . . . . . . . . 8
THE PLANE ANGLE. . . . . . . . . . . . . . . . . . . . . . . 10
PERPENDICULAR AND OBLIQUE LINES. . . . . . . . . . 17
PARALLEL LINES. . . . . . . . . . . . . . . . . . . . . . . . 26
TRIANGLES. . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
LOCI OF POINTS. . . . . . . . . . . . . . . . . . . . . . . . . 48
QUADRILATERALS. . . . . . . . . . . . . . . . . . . . . . . 51
POLYGONS IN GENERAL. . . . . . . . . . . . . . . . . . . . 61
SYMMETRY. . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
EXERCISES. . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
BOOK II. THE CIRCLE. 89
DEFINITIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . 89
ARCS, CHORDS, AND TANGENTS. . . . . . . . . . . . . . 91
MEASUREMENT. . . . . . . . . . . . . . . . . . . . . . . . . 109
THEORY OF LIMITS. . . . . . . . . . . . . . . . . . . . . . . 111
MEASURE OF ANGLES. . . . . . . . . . . . . . . . . . . . . 119
PROBLEMS OF CONSTRUCTION. . . . . . . . . . . . . . . 135
EXERCISES. . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
BOOK III. PROPORTION. SIMILAR POLYGONS. 168
THEORY OF PROPORTION. . . . . . . . . . . . . . . . . . 168
SIMILAR POLYGONS. . . . . . . . . . . . . . . . . . . . . . 183
EXERCISES. . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
NUMERICAL PROPERTIES OF FIGURES. . . . . . . . . . 197
EXERCISES. . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
PROBLEMS OF CONSTRUCTION. . . . . . . . . . . . . . . 210
EXERCISES. . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
BOOK IV. AREAS OF POLYGONS. 226
COMPARISON OF POLYGONS. . . . . . . . . . . . . . . . . 235
EXERCISES. . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
PROBLEMS OF CONSTRUCTION. . . . . . . . . . . . . . . 242
EXERCISES. . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
BOOK V. REGULAR POLYGONS AND CIRCLES. 258
PROBLEMS OF CONSTRUCTION. . . . . . . . . . . . . . . 274
MAXIMA AND MINIMA. . . . . . . . . . . . . . . . . . . . . 282
EXERCISES. . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
TABLE OF FORMULAS. 302
INDEX. 305