8.4 Rotation of Axis 727 Learning Objectives in This Section, You Will: • Identify Nondegenerate Conic Sections Given Their General Form Equations
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Section 6.2 Introduction to Conics: Parabolas 103
Section 6.2 Introduction to Conics: Parabolas 103 Course Number Section 6.2 Introduction to Conics: Parabolas Instructor Objective: In this lesson you learned how to write the standard form of the equation of a parabola. Date Important Vocabulary Define each term or concept. Directrix A fixed line in the plane from which each point on a parabola is the same distance as the distance from the point to a fixed point in the plane. Focus A fixed point in the plane from which each point on a parabola is the same distance as the distance from the point to a fixed line in the plane. Focal chord A line segment that passes through the focus of a parabola and has endpoints on the parabola. Latus rectum The specific focal chord perpendicular to the axis of a parabola. Tangent A line is tangent to a parabola at a point on the parabola if the line intersects, but does not cross, the parabola at the point. I. Conics (Page 433) What you should learn How to recognize a conic A conic section, or conic, is . the intersection of a plane as the intersection of a and a double-napped cone. plane and a double- napped cone Name the four basic conic sections: circle, ellipse, parabola, and hyperbola. In the formation of the four basic conics, the intersecting plane does not pass through the vertex of the cone. When the plane does pass through the vertex, the resulting figure is a(n) degenerate conic , such as . a point, a line, or a pair of intersecting lines. -
Transformation of Axes
19 Chapter 2 Transformation of Axes 2.1 Transformation of Coordinates It sometimes happens that the choice of axes at the beginning of the solution of a problem does not lead to the simplest form of the equation. By a proper transformation of axes an equation may be simplified. This may be accom- plished in two steps, one called translation of axes, the other rotation of axes. 2.1.1 Translation of axes Let ox and oy be the original axes and let o0x0 and o0y0 be the new axes, parallel respectively to the old ones. Also, let o0(h, k) referred to the origin of new axes. Let P be any point in the plane, and let its coordinates referred to the old axes be (x, y) and referred to the new axes be (x0y0) . To determine x and y in terms of x0, y0, h and x = h + x0 y = k + y0 20 Chapter 2. Transformation of Axes these equations represent the equations of translation and hence, the coeffi- cients of the first degree terms are vanish. 2.1.2 Rotation of axes Let ox and oy be the original axes and ox0 and oy0 the new axes. 0 is the origin for each set of axes. Let the angle x0 ox through which the axes have been rotated be represented by q. Let P be any point in the plane, and let its coordinates referred to the old axes be (x, y) and referred to the new axes be (x0, y0), To determine x and y in terms of x0, y0 and q : x = OM = ON − MN = x0 cos q − y0 sin q and y = MP = MM0 + M0P = NN0 + M0P = x0 sin q + y0 cos q 2.1. -
Stable Rationality of Quadric Surface Bundles Over Surfaces
STABLE RATIONALITY OF QUADRIC SURFACE BUNDLES OVER SURFACES BRENDAN HASSETT, ALENA PIRUTKA, AND YURI TSCHINKEL Abstract. We study rationality properties of quadric surface bun- dles over the projective plane. We exhibit families of smooth pro- jective complex fourfolds of this type over connected bases, con- taining both rational and non-rational fibers. 1. Introduction Is a deformation of a smooth rational (or irrational) projective vari- ety still rational (or irrational)? The main goal of this paper is to show that rationality is not deformation invariant for families of smooth com- plex projective varieties of dimension four. Examples along these lines are known when singular fibers are allowed, e.g., smooth cubic three- folds (which are irrational) may specialize to cubic threefolds with or- dinary double points (which are rational), while smooth cubic surfaces (which are rational) may specialize to cones over elliptic curves. Totaro shows that specializations of rational varieties need not be rational in higher dimensions if mild singularities are allowed [Tot16b]. However, de Fernex and Fusi [dFF13] show that the locus of rational fibers in a smooth family of projective complex threefolds is a countable union of closed subsets on the base. Let S be a smooth projective rational surface over the complex num- bers with function field K = C(S). A quadric surface bundle consists of a fourfold X and a flat projective morphism π : X ! S such that the generic fiber Q=K of π is a smooth quadric surface. We assume that π factors through the projectivization of a rank four vector bundle on S such that the fibers are (possibly singular) quadric surfaces; see Section 3 for relevant background. -
Analysis of a Hyperbolic Paraboloid Surface with Curved Edges
ANALYSIS,, OF A HYPERBOLIC PARABOLOID by Carlos Alberto Asturias Theai1 submitted to the Graduate Faculty of the Virginia Polytechnic Institute in candidacy for the degree of MASTER OF SCIENCE in Structural Engineering December 17, 1965 Blacksburg, Virginia · -2- TABLE OF CONTENTS Page I. INTRODUCTION ••••••••••••••••••••••••••••••••••• 5 11. OBJECTIVE •••••••••••••••••••••••••••••••••••••• 8 Ill. HISTORICAL BACKGROUND • ••••••••••••••••••••••••• 9 IV. NOTATION ••••••••••••••••••••••••••••••••••••••• 10 v. METHOD OF ANALYSIS • •••••••••••••••••••••••••••• 12 VI. FORMULATION OF THE METHOD • ••••••••••••••••••••• 15 VII. THEORETICAL INVESTIGATION • ••••••••••••••••••••• 24 A. DEVELOPMENT OF EQUATIONS • •••••••••••••• 24 B. ILLUSTRATIVE EXAMPLE • •••••••••••••••••• 37 VIII. EXPERIMENTAL WORK • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 50 A. DESCRIPTION OF THE MODEL ••••••••••••••• 50 B. TEST SET UP •••••••••••••••••••••••••••• 53 IX. TEST RESULTS AND CONCLUSIONS • •••••••••••••••••• 61 X. BIBLIOGRAPHY ••••••••••••••••••••••••••••••••••• 65 XI. ACKNOWLEDGMENT • •••••••••••••••••••••••••••••••• 67 XII. VITA • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 68 -3- LIST OF FIGURES Page FIGURE I. HYPERBOLIC PARABOLOID TYPES ••••••••••••• 7 FIGURE II. DIFFERENTIAL ELEMENT .................... 13 FIGURE III. AXES .................................... 36 FIGURE IV. DIMENSIONS •••••••••••••••••••••••••••••• 36 FIGURE v. STRESSES ., • 0 ••••••••••••••••••••••••••••• 44 FIGURE VI. STRESSES ••••••••••••••••••••••••••• -
The Pappus Configuration and the Self-Inscribed Octagon
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector MATHEMATICS THE PAPPUS CONFIGURATION AND THE SELF-INSCRIBED OCTAGON. I BY H. S. M. COXETER (Communic&ed at the meeting of April 24, 1976) 1. INTRODUCTION This paper deals with self-dual configurations 8s and 93 in a projective plane, that is, with sets of 8 or 9 points, and the same number of lines, so arranged that each line contains 3 of the points and each point lies on 3 of the lines. Combinatorially there is only one 83, but there are three kinds of 9s. However, we shall discuss only the kind to which the symbol (9s)i was assigned by Hilbert and Cohn-Vossen [24, pp. 91-98; 24a, pp. 103-1111. Both the unique 8s and this particular 9s occur as sub- configurations of the finite projective plane PG(2, 3), which is a 134. The 83 is derived by omitting a point 0, a non-incident line I, all the four points on E, and all the four lines through 0. Similarly, our 9s is derived from the 134 by omitting a point P, a line 1 through P, the remaining three points on I, and the remaining three lines through P. Thus the points of the 83 can be derived from the 9s by omitting any one of its points, but then the lines of the 83 are not precisely a subset of the lines of the 9s. Both configurations occur not only in PG(2, 3) but also in the complex plane, and the 93 occurs in the real plane. -
Geometry I Alexander I
Geometry I Alexander I. Bobenko Draft from February 13, 2017 Preliminary version. Partially extended and partially incomplete. Based on the lecture Geometry I (Winter Semester 2016 TU Berlin). Written by Thilo Rörig based on the Geometry I course and the Lecture Notes of Boris Springborn from WS 2007/08. Acknoledgements: We thank Alina Hinzmann and Jan Techter for the help with preparation of these notes. Contents 1 Introduction 1 2 Projective geometry 3 2.1 Introduction . .3 2.2 Projective spaces . .5 2.2.1 Projective subspaces . .6 2.2.2 Homogeneous and affine coordinates . .7 2.2.3 Models of real projective spaces . .8 2.2.4 Projection of two planes onto each other . 10 2.2.5 Points in general position . 12 2.3 Desargues’ Theorem . 13 2.4 Projective transformations . 15 2.4.1 Central projections and Pappus’ Theorem . 18 2.5 The cross-ratio . 21 2.5.1 Projective involutions of the real projective line . 25 2.6 Complete quadrilateral and quadrangle . 25 2.6.1 Möbius tetrahedra and Koenigs cubes . 29 2.6.2 Projective involutions of the real projective plane . 31 2.7 The fundamental theorem of real projective geometry . 32 2.8 Duality . 35 2.9 Conic sections – The Euclidean point of view . 38 2.9.1 Optical properties of the conic sections . 41 2.10 Conics – The projective point of view . 42 2.11 Pencils of conics . 47 2.12 Rational parametrizations of conics . 49 2.13 The pole-polar relationship, the dual conic and Brianchon’s theorem . 51 2.14 Confocal conics and elliptic billiard . -
APPENDIX E Rotation and the General Second-Degree Equation
APPENDIX E Rotation and the General Second-Degree Equation Rotation of Axes • Invariants Under Rotation y y′ Rotation of Axes In Section 9.1, you learned that equations of conics with axes parallel to one of the coordinate axes can be written in the general form 2 1 2 1 1 1 5 x′ Ax Cy Dx Ey F 0. Horizontal or vertical axes θ Here you will study the equations of conics whose axes are rotated so that they are not x parallel to the x-axis or the y-axis. The general equation for such conics contains an xy-term. Ax2 1 Bxy 1 Cy2 1 Dx 1 Ey 1 F 5 0 Equation in xy-plane To eliminate this xy-term, you can use a procedure called rotation of axes. You want to rotate the x- and y-axes until they are parallel to the axes of the conic. (The rotated axes are denoted as the x9-axis and the y9-axis, as shown in Figure E.1.) After the After rotation of the x- and y-axes counter- rotation has been accomplished, the equation of the conic in the new x9y9-plane will clockwise through an angle u, the rotated have the form axes are denoted as the x9-axis and y9-axis. A9sx9d2 1 C9sy9d2 1 D9x9 1 E9y9 1 F9 5 0. Equation in x9y9-plane Figure E.1 Because this equation has no x9y9-term, you can obtain a standard form by complet- ing the square. The following theorem identifies how much to rotate the axes to eliminate an xy-term and also the equations for determining the new coefficients A9, C9, D9, E9, and F9. -
The Many Faces of Degeneracy in Conic Optimization
Foundations and Trends R in Optimization Vol. XX, No. XX (2017) 1–93 c 2017 DOI: 10.1561/XXXXXXXXXX The many faces of degeneracy in conic optimization last modified on May 9, 2017 Dmitriy Drusvyatskiy Henry Wolkowicz Department of Mathematics Faculty of Mathematics University of Washington University of Waterloo [email protected] [email protected] Contents 1 What this paper is about 2 1.1 Related work . 3 1.2 Outline of the paper . 4 1.3 Reflections on Jonathan Borwein and FR . 4 I Theory 6 2 Convex geometry 7 2.1 Notation . 7 2.2 Facial geometry . 11 2.3 Conic optimization problems . 15 2.4 Commentary . 20 3 Virtues of strict feasibility 21 3.1 Theorem of the alternative . 21 3.2 Stability of the solution . 24 3.3 Distance to infeasibility . 27 3.4 Commentary . 28 4 Facial reduction 29 4.1 Preprocessing in linear programming . 29 ii iii 4.2 Facial reduction in conic optimization . 31 4.3 Facial reduction in semi-definite programming . 32 4.4 What facial reduction actually does . 34 4.5 Singularity degree and the Hölder error bound in SDP . 38 4.6 Towards computation . 39 4.7 Commentary . 40 II Applications and illustrations 42 5 Matrix completions 44 5.1 Positive semi-definite matrix completion . 44 5.2 Euclidean distance matrix completion, EDMC . 50 5.2.1 EDM and SNL with exact data . 54 5.2.2 Extensions to noisy EDM and SNL problems . 55 5.3 Low-rank matrix completions . 56 5.4 Commentary . 60 6 Hard combinatorial problems 61 6.1 Quadratic assignment problem, QAP . -
Introduction to Conic Sections
Introduction to conic sections Author: Eduard Ortega 1 Introduction A conic is a two-dimensional figure created by the intersection of a plane and a right circular cone. All conics can be written in terms of the following equation: Ax2 + Bxy + Cy2 + Dx + Ey + F = 0 : The four conics we'll explore in this text are parabolas, ellipses, circles, and hyperbolas. The equations for each of these conics can be written in a standard form, from which a lot about the given conic can be told without having to graph it. We'll study the standard forms and graphs of these four conics, 1.1 General definition A conic is the intersection of a plane and a right circular cone. The four basic types of conics are parabolas, ellipses, circles, and hyperbolas. Study the figures below to see how a conic is geometrically defined. In a non-degenerate conic the plane does not pass through the vertex of the cone. When the plane does intersect the vertex of the cone, the resulting conic is called a degenerate conic. Degenerate conics include a point, a line, and two intersecting lines. The equation of every conic can be written in the following form: Ax2 + Bxy + Cy2 + Dx + Ey + F = 0 : 1 This is the algebraic definition of a conic. Conics can be classified according to the coefficients of this equation. The discriminant of the equation is B2 − 4AC. Assuming a conic is not degenerate, the following conditions hold true: 1. If B2 − 4AC < 0 , the conic is a circle (if B = 0 and A = B), or an ellipse. -
Rotation of Axes
ROTATION OF AXES ■■ For a discussion of conic sections, see In precalculus or calculus you may have studied conic sections with equations of the form Calculus, Early Transcendentals, Sixth Edition, Section 10.5. Ax2 ϩ Cy2 ϩ Dx ϩ Ey ϩ F 0 Here we show that the general second-degree equation 1 Ax2 ϩ Bxy ϩ Cy2 ϩ Dx ϩ Ey ϩ F 0 can be analyzed by rotating the axes so as to eliminate the term Bxy. In Figure 1 the x and y axes have been rotated about the origin through an acute angle to produce the X and Y axes. Thus, a given point P has coordinates ͑x, y͒ in the first coor- dinate system and ͑X, Y͒ in the new coordinate system. To see how X and Y are related to x and y we observe from Figure 2 that X r cos Y r sin x r cos͑ ϩ ͒ y r sin͑ ϩ ͒ y y Y P(x, y) Y P(X, Y) P X Y X r y ˙ ¨ ¨ 0 x 0 x X x FIGURE 1 FIGURE 2 The addition formula for the cosine function then gives x r cos͑ ϩ ͒ r͑cos cos Ϫ sin sin ͒ ͑r cos ͒ cos Ϫ ͑r sin ͒ sin ⌾ cos Ϫ Y sin A similar computation gives y in terms of X and Y and so we have the following formulas: 2 x X cos Ϫ Y sin y X sin ϩ Y cos By solving Equations 2 for X and Y we obtain 3 X x cos ϩ y sin Y Ϫx sin ϩ y cos EXAMPLE 1 If the axes are rotated through 60Њ, find the XY-coordinates of the point whose xy-coordinates are ͑2, 6͒. -
Rotation of Axes 1 Rotation of Axes
Rotation of Axes 1 Rotation of Axes At the beginning of Chapter 5 we stated that all equations of the form Ax2 + Bxy + Cy2 + Dx + Ey + F =0 represented a conic section, which might possibly be degenerate. We saw in Section 5.2 that the graph of the quadratic equation Ax2 + Cy2 + Dx + Ey + F =0 is a parabola when A =0orC = 0, that is, when AC = 0. In Section 5.3 we found that the graph is an ellipse if AC > 0, and in Section 5.4 we saw that the graph is a hyperbola when AC < 0. So we have classified the situation when B = 0. Degenerate situations can occur; for example, the quadratic equation x2 + y2 + 1 = 0 has no solutions, and the graph of x2 − y2 = 0 is not a hyperbola, but the pair of lines with equations y = x. But excepting this type of situation, we have categorized the graphs of all the quadratic equations with B =0. When B =6 0, a rotation can be performed to bring the conic into a form that will allow us to compare it with one that is in standard position. To set up the discussion, letusfirstsupposethatasetofxy-coordinate axes has been rotated about the origin by an angle θ, where 0 <θ<π=2, to form a new set ofx ^y^-axes, as shown in Figure 1(a). We would like to determine the coordinates for a point P in the plane relative to the two coordinate systems. y y yˆ yˆ P(x, y) P(xˆˆ, y) P(x, y) P(xˆˆ, y) r xˆ r xˆ B f B u u A x A x (a) (b) Figure 1 2 CHAPTER 5 Conic Sections, Polar Coordinates, and Parametric Equations First introduce a new pair of variables r and φ to represent, respectively, the distance from P to the origin and the angle formed by thex ^-axis and the line connecting the origin to P , as shown in Figure 1(b). -
Rotation of Axes
ROTATION OF AXES ■■ For a discussion of conic sections, see In precalculus or calculus you may have studied conic sections with equations of the form Review of Conic Sections. Ax2 ϩ Cy2 ϩ Dx ϩ Ey ϩ F 0 Here we show that the general second-degree equation 1 Ax2 ϩ Bxy ϩ Cy2 ϩ Dx ϩ Ey ϩ F 0 can be analyzed by rotating the axes so as to eliminate the term Bxy. In Figure 1 the x and y axes have been rotated about the origin through an acute angle to produce the X and Y axes. Thus, a given point P has coordinates ͑x, y͒ in the first coor- dinate system and ͑X, Y͒ in the new coordinate system. To see how X and Y are related to x and y we observe from Figure 2 that X r cos Y r sin x r cos͑ ϩ ͒ y r sin͑ ϩ ͒ y y Y P(x, y) Y P(X, Y) P X Y X r y ˙ ¨ ¨ 0 x 0 x X x FIGURE 1 FIGURE 2 The addition formula for the cosine function then gives x r cos͑ ϩ ͒ r͑cos cos Ϫ sin sin ͒ ͑r cos ͒ cos Ϫ ͑r sin ͒ sin ⌾ cos Ϫ Y sin A similar computation gives y in terms of X and Y and so we have the following formulas: 2 x X cos Ϫ Y sin y X sin ϩ Y cos By solving Equations 2 for X and Y we obtain 3 X x cos ϩ y sin Y Ϫx sin ϩ y cos EXAMPLE 1 If the axes are rotated through 60Њ, find the XY-coordinates of the point whose xy-coordinates are ͑2, 6͒.