Shadows Of The Circle: Conic Sections, Optimal Figures And Non-Euclidean Geometry 9789810234188, 981023418X
The aim of this book is to throw light on various facets of geometry through development of four geometrical themes. The
282 22 2MB
English Pages 118 [119] Year 1998
Table of contents :
Front Cover
Title Page
Copyright Page
Preface
Table of Contents
Chapter 1: An ellipse in the shadow
The ellipse as a plane section of a cylinder
The equation of the ellipse
A parametrization of the ellipse
The ellipse as a locus
Directrix for the ellipse
Geometrical determination of foci and directrices for the ellipse
The tangents of the ellipse
An application to gear wheel movements
Sources for Chapter 1
Chapter 2: With conic sections in the light
The ellipse as a plane section in a cone
Geometric determination of foci and directrices for a conic section
The parabola
The hyperbola
Hyperbolic navigational systems
Conic sections as algebraic curves
Epilogue
Sources for Chapter 2
Chapter 3: Optimal plane figures
Isosceles triangles
Perrons paradox
Some simple geometrical problems without solutions
A fundamental property of the real numbers
Maxima and minima of real-valued functions
The equilateral triangle as optimal figure
The square as optimal figure
The regular polygons as optimal figures
Some limit values for regular polygons
The isoperimetric problem
Epilogue: Elements of the history of the calculus of variations
Sources for Chapter 3
Chapter 4: The Poincare disc model of non-Euclidean geometry
Euclids Elements
The parallel axiom and non-Euclidean geometries
Inversion in a circle
Inversion as a mapping
Orthogonal circles and Euclids Postulate 1 in the hyperbolic plane
The notion of distance in the hyperbolic plane and Euclids Postulate 2
Isometries in the hyperbolic plane
Hyperbolic triangles and n-gons
The Poincare half-plane
Elliptic geometries
Sources for Chapter 4
Exercises
Index
Front Cover
Title Page
Copyright Page
Preface
Table of Contents
Chapter 1: An ellipse in the shadow
The ellipse as a plane section of a cylinder
The equation of the ellipse
A parametrization of the ellipse
The ellipse as a locus
Directrix for the ellipse
Geometrical determination of foci and directrices for the ellipse
The tangents of the ellipse
An application to gear wheel movements
Sources for Chapter 1
Chapter 2: With conic sections in the light
The ellipse as a plane section in a cone
Geometric determination of foci and directrices for a conic section
The parabola
The hyperbola
Hyperbolic navigational systems
Conic sections as algebraic curves
Epilogue
Sources for Chapter 2
Chapter 3: Optimal plane figures
Isosceles triangles
Perrons paradox
Some simple geometrical problems without solutions
A fundamental property of the real numbers
Maxima and minima of real-valued functions
The equilateral triangle as optimal figure
The square as optimal figure
The regular polygons as optimal figures
Some limit values for regular polygons
The isoperimetric problem
Epilogue: Elements of the history of the calculus of variations
Sources for Chapter 3
Chapter 4: The Poincare disc model of non-Euclidean geometry
Euclids Elements
The parallel axiom and non-Euclidean geometries
Inversion in a circle
Inversion as a mapping
Orthogonal circles and Euclids Postulate 1 in the hyperbolic plane
The notion of distance in the hyperbolic plane and Euclids Postulate 2
Isometries in the hyperbolic plane
Hyperbolic triangles and n-gons
The Poincare half-plane
Elliptic geometries
Sources for Chapter 4
Exercises
Index
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