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A Study of Dandelin Spheres: a Second Year Investigation
CALIFORNIA STATE SCIENCE FAIR 2009 PROJECT SUMMARY Name(s) Project Number Sundeep Bekal S1602 Project Title A Study of Dandelin Spheres: A Second Year Investigation Abstract Objectives/Goals The purpose of this investigation is to see if there is a relationship that forms between the radius of the smaller dandelin sphere to the tangent of the angle RLM and distances that form inside the ellipse. Methods/Materials I investigated a conic section of an ellipse that contained two Dandelin Spheres to determine if there was such a relationship. I used the same program as last year, Geometer's Sketchpad, to generate measurements of last year's 2D model of the conic section so that I could better investigate the relationship. After slicing the spheres along the central pole, I looked to see if there were any patterns or relationships. To do this I set the radius of the smaller circle (sphere in 3-D) to 1.09 cm. I changed the radius by .05 cm every time while also noting how the other segments changed or did not change. Materials -Geometer's Sketchpad -Calculator -Computer -Paper -Pencil Results After looking through the data tables I noticed that the radius had the same exact values as (a+c)(tan(1/2) angleRLM), where (a+c) is the distance located in the ellipse. I also noticed that the ratio of the (radius)/(a+c) had the same values as tan((1/2 angleRLM)). I figured that this would be true because the tan (theta)=(opposite)/(adjacent) which in this case, would be tan ((1/2 angleRLM)) = (radius)/(a+c). -
Chapter 11. Three Dimensional Analytic Geometry and Vectors
Chapter 11. Three dimensional analytic geometry and vectors. Section 11.5 Quadric surfaces. Curves in R2 : x2 y2 ellipse + =1 a2 b2 x2 y2 hyperbola − =1 a2 b2 parabola y = ax2 or x = by2 A quadric surface is the graph of a second degree equation in three variables. The most general such equation is Ax2 + By2 + Cz2 + Dxy + Exz + F yz + Gx + Hy + Iz + J =0, where A, B, C, ..., J are constants. By translation and rotation the equation can be brought into one of two standard forms Ax2 + By2 + Cz2 + J =0 or Ax2 + By2 + Iz =0 In order to sketch the graph of a quadric surface, it is useful to determine the curves of intersection of the surface with planes parallel to the coordinate planes. These curves are called traces of the surface. Ellipsoids The quadric surface with equation x2 y2 z2 + + =1 a2 b2 c2 is called an ellipsoid because all of its traces are ellipses. 2 1 x y 3 2 1 z ±1 ±2 ±3 ±1 ±2 The six intercepts of the ellipsoid are (±a, 0, 0), (0, ±b, 0), and (0, 0, ±c) and the ellipsoid lies in the box |x| ≤ a, |y| ≤ b, |z| ≤ c Since the ellipsoid involves only even powers of x, y, and z, the ellipsoid is symmetric with respect to each coordinate plane. Example 1. Find the traces of the surface 4x2 +9y2 + 36z2 = 36 1 in the planes x = k, y = k, and z = k. Identify the surface and sketch it. Hyperboloids Hyperboloid of one sheet. The quadric surface with equations x2 y2 z2 1. -
Calculus & Analytic Geometry
TQS 126 Spring 2008 Quinn Calculus & Analytic Geometry III Quadratic Equations in 3-D Match each function to its graph 1. 9x2 + 36y2 +4z2 = 36 2. 4x2 +9y2 4z2 =0 − 3. 36x2 +9y2 4z2 = 36 − 4. 4x2 9y2 4z2 = 36 − − 5. 9x2 +4y2 6z =0 − 6. 9x2 4y2 6z =0 − − 7. 4x2 + y2 +4z2 4y 4z +36=0 − − 8. 4x2 + y2 +4z2 4y 4z 36=0 − − − cone • ellipsoid • elliptic paraboloid • hyperbolic paraboloid • hyperboloid of one sheet • hyperboloid of two sheets 24 TQS 126 Spring 2008 Quinn Calculus & Analytic Geometry III Parametric Equations (§10.1) and Vector Functions (§13.1) Definition. If x and y are given as continuous function x = f(t) y = g(t) over an interval of t-values, then the set of points (x, y)=(f(t),g(t)) defined by these equation is a parametric curve (sometimes called aplane curve). The equations are parametric equations for the curve. Often we think of parametric curves as describing the movement of a particle in a plane over time. Examples. x = 2cos t x = et 0 t π 1 t e y = 3sin t ≤ ≤ y = ln t ≤ ≤ Can we find parameterizations of known curves? the line segment circle x2 + y2 =1 from (1, 3) to (5, 1) Why restrict ourselves to only moving through planes? Why not space? And why not use our nifty vector notation? 25 Definition. If x, y, and z are given as continuous functions x = f(t) y = g(t) z = h(t) over an interval of t-values, then the set of points (x,y,z)= (f(t),g(t), h(t)) defined by these equation is a parametric curve (sometimes called a space curve). -
Structural Forms 1
Key principles The hyperboloid of revolution is a Surface and may be generated by revolving a Hyperbola about its conjugate axis. The outline of the elevation will be a Hyperbola. When the conjugate axis is vertical all horizontal sections are circles. The horizontal section at the mid point of the conjugate axis is known as the Throat. The diagram shows the incomplete construction for drawing a hyperbola in a rectangle. (a) Draw the outline of the both branches of the double hyperbola in the rectangle. The diagram shows the incomplete Elevation of a hyperboloid of revolution. (a) Determine the position of the throat circle in elevation. (b) Draw the outline of the both branches of the double hyperbola in elevation. DESIGN & COMMUNICATION GRAPHICS Structural forms 1 NAME: ______________________________ DATE: _____________ The diagram shows the plan and incomplete elevation of an object based on the hyperboloid of revolution. The focal points and transverse axis of the hyperbola are also shown. (a) Using the given information draw the outline of the elevation.. F The diagram shows the axis, focal points and transverse axis of a double hyperbola. (a) Draw the outline of both branches of the double hyperbola. (b) The difference between the focal distances for any point on a double hyperbola is constant and equal to the length of the transverse axis. (c) Indicate this principle on the drawing below. DESIGN & COMMUNICATION GRAPHICS Structural forms 2 NAME: ______________________________ DATE: _____________ Key principles The diagram shows the plan and incomplete elevation of a hyperboloid of revolution. The hyperboloid of revolution may also be generated by revolving one skew line about another. -
Quadric Surfaces
Quadric Surfaces Six basic types of quadric surfaces: • ellipsoid • cone • elliptic paraboloid • hyperboloid of one sheet • hyperboloid of two sheets • hyperbolic paraboloid (A) (B) (C) (D) (E) (F) 1. For each surface, describe the traces of the surface in x = k, y = k, and z = k. Then pick the term from the list above which seems to most accurately describe the surface (we haven't learned any of these terms yet, but you should be able to make a good educated guess), and pick the correct picture of the surface. x2 y2 (a) − = z. 9 16 1 • Traces in x = k: parabolas • Traces in y = k: parabolas • Traces in z = k: hyperbolas (possibly a pair of lines) y2 k2 Solution. The trace in x = k of the surface is z = − 16 + 9 , which is a downward-opening parabola. x2 k2 The trace in y = k of the surface is z = 9 − 16 , which is an upward-opening parabola. x2 y2 The trace in z = k of the surface is 9 − 16 = k, which is a hyperbola if k 6= 0 and a pair of lines (a degenerate hyperbola) if k = 0. This surface is called a hyperbolic paraboloid , and it looks like picture (E) . It is also sometimes called a saddle. x2 y2 z2 (b) + + = 1. 4 25 9 • Traces in x = k: ellipses (possibly a point) or nothing • Traces in y = k: ellipses (possibly a point) or nothing • Traces in z = k: ellipses (possibly a point) or nothing y2 z2 k2 k2 Solution. The trace in x = k of the surface is 25 + 9 = 1− 4 . -
(Anti-)De Sitter Space-Time
Geometry of (Anti-)De Sitter space-time Author: Ricard Monge Calvo. Facultat de F´ısica, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain. Advisor: Dr. Jaume Garriga Abstract: This work is an introduction to the De Sitter and Anti-de Sitter spacetimes, as the maximally symmetric constant curvature spacetimes with positive and negative Ricci curvature scalar R. We discuss their causal properties and the characterization of their geodesics, and look at p;q the spaces embedded in flat R spacetimes with an additional dimension. We conclude that the geodesics in these spaces can be regarded as intersections with planes going through the origin of the embedding space, and comment on the consequences. I. INTRODUCTION In the case of dS4, introducing the coordinates (T; χ, θ; φ) given by: Einstein's general relativity postulates that spacetime T T is a differential (Lorentzian) manifold of dimension 4, X0 = a sinh X~ = a cosh ~n (4) a a whose Ricci curvature tensor is determined by its mass- energy contents, according to the equations: where X~ = X1;X2;X3;X4 and ~n = ( cos χ, sin χ cos θ, sin χ sin θ cos φ, sin χ sin θ sin φ) with T 2 (−∞; 1), 0 ≤ 1 8πG χ ≤ π, 0 ≤ θ ≤ π and 0 ≤ φ ≤ 2π, then the line element Rµλ − Rgµλ + Λgµλ = 4 Tµλ (1) 2 c is: where Rµλ is the Ricci curvature tensor, R te Ricci scalar T ds2 = −dT 2 + a2 cosh2 [dχ2 + sin2 χ dΩ2] (5) curvature, gµλ the metric tensor, Λ the cosmological con- a 2 stant, G the universal gravitational constant, c the speed of light in vacuum and Tµλ the energy-momentum ten- where the surfaces of constant time dT = 0 have metric 2 2 2 2 sor. -
A Human Introduction to Geometry Spring 2017 UM Da Vinci Program Drew Armstrong
A Human Introduction to Geometry Spring 2017 UM da Vinci Program Drew Armstrong Contents 1 The Pythagorean Tradition? 2 1.1 Pythagoras and 2.................................. 2 1.2 Plato and Regular Polyhedra . 9 1.3 Kepler and Conic Sections . 18 2 Euclidean and Non-Euclidean Geometry 29 2.1 The Deductive Method . 29 2.2 Euclid's Elements ................................... 32 2.3 Selections from Book I . 40 2.4 Triangles and Curvature . 48 3 The Problem of Measurement 60 3.1 Pure and Applied Mathematics . 60 3.2 Eudoxus' Theory of Proportion . 63 3.3 Archimedes and the Existence of π ......................... 70 3.4 Trigonometry is Hard . 83 3.5 Rigorous and Intuitive Mathematics . 105 3.6 Impossible Problems . 109 4 Coordinate Geometry and Transformations 110 5 Projective Geometry 110 Introduction Geometry is the most human of mathematical pursuits; so much so that it was regarded as insufficiently rigorous for twentieth century tastes and was largely banished from the under- graduate curriculum. This is a shame because drawing and looking at pictures are excellent ways to engage students. Visual intuition is also the primary way that we can hack our pri- mate architecture, to allow us to make progress in more abstract kinds of mathematics that would otherwise be impossible to comprehend. In this class we will embrace the human side of mathematics by following the story of geometry|pure and applied|through the ages. On the applied side we will follow geom- etry from its earliest use in land measurement, through the discovery of perspective drawing in the Renaissance, to its use today in computer graphics. -
Surfaces in 3-Space
Differential Geometry of Some SURFACES IN 3-SPACE Nicholas Wheeler December 2015 Introduction. Recent correspondence with Ahmed Sebbar concerning the theory of unimodular 3 3 circulant matrices1 × x y z det z x y = x3 + y3 + z3 3xyz = 1 y z x − brought to my attention a surface Σ in R3 which, I was informed, is encountered in work of H. Jonas (1915, 1921) and, because of its form when plotted, is known as “Jonas’ hexenhut” (witch’s hat). I was led by Google from “hexenhut” to a monograph B¨acklund and Darboux Transformations: Geometry and Modern Applications in Soliton Theory, by C. Rogers & W. K. Schief (2002). These are subjects in which I have had longstanding interest, but which I have not thought about for many years. I am inspired by those authors’ splendid book to revisit this subject area. In part one I assemble the tools that play essential roles in the theory of surfaces in R3, and in part two use those tools to develop the properties of some specific surfaces—particularly the pseudosphere, because it was the cradle in which was born the sine-Gordon equation, which a century later became central to the physical theory of solitons.2 part one Concepts & Tools Essential to the Theory of Surfaces in 3-Space Fundamental forms. Relative to a Cartesian frame in R3, surfaces Σ can be described implicitly f(x, y, z) = 0 but for the purposes of differential geometry must be described parametrically x(u, v) r(u, v) = y(u, v) z(u, v) 1 See “Simplest generalization of Pell’s Problem,” (September, 2015). -
11.5: Quadric Surfaces
c Dr Oksana Shatalov, Spring 2013 1 11.5: Quadric surfaces REVIEW: Parabola, hyperbola and ellipse. • Parabola: y = ax2 or x = ay2. y y x x 0 0 y x2 y2 • Ellipse: + = 1: x a2 b2 0 Intercepts: (±a; 0)&(0; ±b) x2 y2 x2 y2 • Hyperbola: − = 1 or − + = 1 a2 b2 a2 b2 y y x x 0 0 Intercepts: (±a; 0) Intercepts: (0; ±b) c Dr Oksana Shatalov, Spring 2013 2 The most general second-degree equation in three variables x; y and z: 2 2 2 Ax + By + Cz + axy + bxz + cyz + d1x + d2y + d3z + E = 0; (1) where A; B; C; a; b; c; d1; d2; d3;E are constants. The graph of (1) is a quadric surface. Note if A = B = C = a = b = c = 0 then (1) is a linear equation and its graph is a plane (this is the case of degenerated quadric surface). By translations and rotations (1) can be brought into one of the two standard forms: Ax2 + By2 + Cz2 + J = 0 or Ax2 + By2 + Iz = 0: In order to sketch the graph of a surface determine the curves of intersection of the surface with planes parallel to the coordinate planes. The obtained in this way curves are called traces or cross-sections of the surface. Quadric surfaces can be classified into 5 categories: ellipsoids, hyperboloids, cones, paraboloids, quadric cylinders. (shown in the table, see Appendix.) The elements which characterize each of these categories: 1. Standard equation. 2. Traces (horizontal ( by planes z = k), yz-traces (by x = 0) and xz-traces (by y = 0). -
Tilted Planes and Curvature in Three-Dimensional Space: Explorations of Partial Derivatives
Tilted Planes and Curvature in Three-Dimensional Space: Explorations of Partial Derivatives By Andrew Grossfield, Ph. D., P. E. Abstract Many engineering students encounter and algebraically manipulate partial derivatives in their fluids, thermodynamics or electromagnetic wave theory courses. However it is possible that unless these students were properly introduced to these symbols, they may lack the insight that could be obtained from a geometric or visual approach to the equations that contain these symbols. We accept the approach that just as the direction of a curve at a point in two-dimensional space is described by the slope of the straight line tangent to the curve at that point, the orientation of a surface at a point in 3-dimensional space is determined by the orientation of the plane tangent to the surface at that point. A straight line has only one direction described by the same slope everywhere along its length; a tilted plane has the same orientation everywhere but has many slopes at each point. In fact the slope in almost every direction leading away from a point is different. How do we conceive of these differing slopes and how can they be evaluated? We are led to conclude that the derivative of a multivariable function is the gradient vector, and that it is wrong and misleading to define the gradient in terms of some kind of limiting process. This approach circumvents the need for all the unnecessary delta-epsilon arguments about obvious results, while providing visual insight into properties of multi-variable derivatives and differentials. This paper provides the visual connection displaying the remarkably simple and beautiful relationships between the gradient, the directional derivatives and the partial derivatives. -