Non-Euclidean Geometry Rick Roesler
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Proofs with Perpendicular Lines
3.4 Proofs with Perpendicular Lines EEssentialssential QQuestionuestion What conjectures can you make about perpendicular lines? Writing Conjectures Work with a partner. Fold a piece of paper D in half twice. Label points on the two creases, as shown. a. Write a conjecture about AB— and CD — . Justify your conjecture. b. Write a conjecture about AO— and OB — . AOB Justify your conjecture. C Exploring a Segment Bisector Work with a partner. Fold and crease a piece A of paper, as shown. Label the ends of the crease as A and B. a. Fold the paper again so that point A coincides with point B. Crease the paper on that fold. b. Unfold the paper and examine the four angles formed by the two creases. What can you conclude about the four angles? B Writing a Conjecture CONSTRUCTING Work with a partner. VIABLE a. Draw AB — , as shown. A ARGUMENTS b. Draw an arc with center A on each To be prof cient in math, side of AB — . Using the same compass you need to make setting, draw an arc with center B conjectures and build a on each side of AB— . Label the C O D logical progression of intersections of the arcs C and D. statements to explore the c. Draw CD — . Label its intersection truth of your conjectures. — with AB as O. Write a conjecture B about the resulting diagram. Justify your conjecture. CCommunicateommunicate YourYour AnswerAnswer 4. What conjectures can you make about perpendicular lines? 5. In Exploration 3, f nd AO and OB when AB = 4 units. -
Using Non-Euclidean Geometry to Teach Euclidean Geometry to K–12 Teachers
Using non-Euclidean Geometry to teach Euclidean Geometry to K–12 teachers David Damcke Department of Mathematics, University of Portland, Portland, OR 97203 [email protected] Tevian Dray Department of Mathematics, Oregon State University, Corvallis, OR 97331 [email protected] Maria Fung Mathematics Department, Western Oregon University, Monmouth, OR 97361 [email protected] Dianne Hart Department of Mathematics, Oregon State University, Corvallis, OR 97331 [email protected] Lyn Riverstone Department of Mathematics, Oregon State University, Corvallis, OR 97331 [email protected] January 22, 2008 Abstract The Oregon Mathematics Leadership Institute (OMLI) is an NSF-funded partner- ship aimed at increasing mathematics achievement of students in partner K–12 schools through the creation of sustainable leadership capacity. OMLI’s 3-week summer in- stitute offers content and leadership courses for in-service teachers. We report here on one of the content courses, entitled Comparing Different Geometries, which en- hances teachers’ understanding of the (Euclidean) geometry in the K–12 curriculum by studying two non-Euclidean geometries: taxicab geometry and spherical geometry. By confronting teachers from mixed grade levels with unfamiliar material, while mod- eling protocol-based pedagogy intended to emphasize a cooperative, risk-free learning environment, teachers gain both content knowledge and insight into the teaching of mathematical thinking. Keywords: Cooperative groups, Euclidean geometry, K–12 teachers, Norms and protocols, Rich mathematical tasks, Spherical geometry, Taxicab geometry 1 1 Introduction The Oregon Mathematics Leadership Institute (OMLI) is a Mathematics/Science Partner- ship aimed at increasing mathematics achievement of K–12 students by providing professional development opportunities for in-service teachers. -
And Are Lines on Sphere B That Contain Point Q
11-5 Spherical Geometry Name each of the following on sphere B. 3. a triangle SOLUTION: are examples of triangles on sphere B. 1. two lines containing point Q SOLUTION: and are lines on sphere B that contain point Q. ANSWER: 4. two segments on the same great circle SOLUTION: are segments on the same great circle. ANSWER: and 2. a segment containing point L SOLUTION: is a segment on sphere B that contains point L. ANSWER: SPORTS Determine whether figure X on each of the spheres shown is a line in spherical geometry. 5. Refer to the image on Page 829. SOLUTION: Notice that figure X does not go through the pole of ANSWER: the sphere. Therefore, figure X is not a great circle and so not a line in spherical geometry. ANSWER: no eSolutions Manual - Powered by Cognero Page 1 11-5 Spherical Geometry 6. Refer to the image on Page 829. 8. Perpendicular lines intersect at one point. SOLUTION: SOLUTION: Notice that the figure X passes through the center of Perpendicular great circles intersect at two points. the ball and is a great circle, so it is a line in spherical geometry. ANSWER: yes ANSWER: PERSEVERANC Determine whether the Perpendicular great circles intersect at two points. following postulate or property of plane Euclidean geometry has a corresponding Name two lines containing point M, a segment statement in spherical geometry. If so, write the containing point S, and a triangle in each of the corresponding statement. If not, explain your following spheres. reasoning. 7. The points on any line or line segment can be put into one-to-one correspondence with real numbers. -
Geometry: Euclid and Beyond, by Robin Hartshorne, Springer-Verlag, New York, 2000, Xi+526 Pp., $49.95, ISBN 0-387-98650-2
BULLETIN (New Series) OF THE AMERICAN MATHEMATICAL SOCIETY Volume 39, Number 4, Pages 563{571 S 0273-0979(02)00949-7 Article electronically published on July 9, 2002 Geometry: Euclid and beyond, by Robin Hartshorne, Springer-Verlag, New York, 2000, xi+526 pp., $49.95, ISBN 0-387-98650-2 1. Introduction The first geometers were men and women who reflected on their experiences while doing such activities as building small shelters and bridges, making pots, weaving cloth, building altars, designing decorations, or gazing into the heavens for portentous signs or navigational aides. Main aspects of geometry emerged from three strands of early human activity that seem to have occurred in most cultures: art/patterns, navigation/stargazing, and building structures. These strands developed more or less independently into varying studies and practices that eventually were woven into what we now call geometry. Art/Patterns: To produce decorations for their weaving, pottery, and other objects, early artists experimented with symmetries and repeating patterns. Later the study of symmetries of patterns led to tilings, group theory, crystallography, finite geometries, and in modern times to security codes and digital picture com- pactifications. Early artists also explored various methods of representing existing objects and living things. These explorations led to the study of perspective and then projective geometry and descriptive geometry, and (in the 20th century) to computer-aided graphics, the study of computer vision in robotics, and computer- generated movies (for example, Toy Story ). Navigation/Stargazing: For astrological, religious, agricultural, and other purposes, ancient humans attempted to understand the movement of heavenly bod- ies (stars, planets, Sun, and Moon) in the apparently hemispherical sky. -
Project 2: Euclidean & Spherical Geometry Applied to Course Topics
Project 2: Euclidean & Spherical Geometry Applied to Course Topics You may work alone or with one other person. During class you will write down your top problems (unranked) and from this you will be assigned one problem. In this project, we will use intuition from previous Euclidean geometry knowledge along with experiences from hands-on models and/or research. The purpose of this assignment is an introduction to the concepts in the course syllabus as we explore diverse geometric perspectives. Project Components: a) Review content related to your problem that applies to the geometry of the plane / Euclidean geometry / flat geometry. For example, if you have Problem 1 then you might review the definitions of lines and how to calculate them, for Problem 9 you might review some information related to area and surface area, for Problem 10 you might review coordinate systems... You may use our book, the internet, or other sources. b) Why the topic is important in mathematics and the real-world? Conduct searches like \trian- gles are important" or a search word related to your problem and then (with and without quotations) words like important, interesting, useful, or real-life applications. You might also pick some specific fields to see if there are applications such as: Pythagorean theorem chemistry c) Summarize diverse spherical perspectives. You do not need to prove an answer or completely resolve the issue on the sphere. You should look for various perspectives related to spherical geometry, and summarize those in your own words. Try different combinations of search terms related to your problem along with words like sphere, spherical, earth, or spherical geometry. -
Positional Astronomy Coordinate Systems
Positional Astronomy Observational Astronomy 2019 Part 2 Prof. S.C. Trager Coordinate systems We need to know where the astronomical objects we want to study are located in order to study them! We need a system (well, many systems!) to describe the positions of astronomical objects. The Celestial Sphere First we need the concept of the celestial sphere. It would be nice if we knew the distance to every object we’re interested in — but we don’t. And it’s actually unnecessary in order to observe them! The Celestial Sphere Instead, we assume that all astronomical sources are infinitely far away and live on the surface of a sphere at infinite distance. This is the celestial sphere. If we define a coordinate system on this sphere, we know where to point! Furthermore, stars (and galaxies) move with respect to each other. The motion normal to the line of sight — i.e., on the celestial sphere — is called proper motion (which we’ll return to shortly) Astronomical coordinate systems A bit of terminology: great circle: a circle on the surface of a sphere intercepting a plane that intersects the origin of the sphere i.e., any circle on the surface of a sphere that divides that sphere into two equal hemispheres Horizon coordinates A natural coordinate system for an Earth- bound observer is the “horizon” or “Alt-Az” coordinate system The great circle of the horizon projected on the celestial sphere is the equator of this system. Horizon coordinates Altitude (or elevation) is the angle from the horizon up to our object — the zenith, the point directly above the observer, is at +90º Horizon coordinates We need another coordinate: define a great circle perpendicular to the equator (horizon) passing through the zenith and, for convenience, due north This line of constant longitude is called a meridian Horizon coordinates The azimuth is the angle measured along the horizon from north towards east to the great circle that intercepts our object (star) and the zenith. -
Spherical Geometry
987023 2473 < % 52873 52 59 3 1273 ¼4 14 578 2 49873 3 4 7∆��≌ ≠ 3 δ � 2 1 2 7 5 8 4 3 23 5 1 ⅓β ⅝Υ � VCAA-AMSI maths modules 5 1 85 34 5 45 83 8 8 3 12 5 = 2 38 95 123 7 3 7 8 x 3 309 �Υβ⅓⅝ 2 8 13 2 3 3 4 1 8 2 0 9 756 73 < 1 348 2 5 1 0 7 4 9 9 38 5 8 7 1 5 812 2 8 8 ХФУШ 7 δ 4 x ≠ 9 3 ЩЫ � Ѕ � Ђ 4 � ≌ = ⅙ Ё ∆ ⊚ ϟϝ 7 0 Ϛ ό ¼ 2 ύҖ 3 3 Ҧδ 2 4 Ѽ 3 5 ᴂԅ 3 3 Ӡ ⍰1 ⋓ ӓ 2 7 ӕ 7 ⟼ ⍬ 9 3 8 Ӂ 0 ⤍ 8 9 Ҷ 5 2 ⋟ ҵ 4 8 ⤮ 9 ӛ 5 ₴ 9 4 5 € 4 ₦ € 9 7 3 ⅘ 3 ⅔ 8 2 2 0 3 1 ℨ 3 ℶ 3 0 ℜ 9 2 ⅈ 9 ↄ 7 ⅞ 7 8 5 2 ∭ 8 1 8 2 4 5 6 3 3 9 8 3 8 1 3 2 4 1 85 5 4 3 Ӡ 7 5 ԅ 5 1 ᴂ - 4 �Υβ⅓⅝ 0 Ѽ 8 3 7 Ҧ 6 2 3 Җ 3 ύ 4 4 0 Ω 2 = - Å 8 € ℭ 6 9 x ℗ 0 2 1 7 ℋ 8 ℤ 0 ∬ - √ 1 ∜ ∱ 5 ≄ 7 A guide for teachers – Years 11 and 12 ∾ 3 ⋞ 4 ⋃ 8 6 ⑦ 9 ∭ ⋟ 5 ⤍ ⅞ Geometry ↄ ⟼ ⅈ ⤮ ℜ ℶ ⍬ ₦ ⍰ ℨ Spherical Geometry ₴ € ⋓ ⊚ ⅙ ӛ ⋟ ⑦ ⋃ Ϛ ό ⋞ 5 ∾ 8 ≄ ∱ 3 ∜ 8 7 √ 3 6 ∬ ℤ ҵ 4 Ҷ Ӂ ύ ӕ Җ ӓ Ӡ Ҧ ԅ Ѽ ᴂ 8 7 5 6 Years DRAFT 11&12 DRAFT Spherical Geometry – A guide for teachers (Years 11–12) Andrew Stewart, Presbyterian Ladies’ College, Melbourne Illustrations and web design: Catherine Tan © VCAA and The University of Melbourne on behalf of AMSI 2015. -
08. Non-Euclidean Geometry 1
Topics: 08. Non-Euclidean Geometry 1. Euclidean Geometry 2. Non-Euclidean Geometry 1. Euclidean Geometry • The Elements. ~300 B.C. ~100 A.D. Earliest existing copy 1570 A.D. 1956 First English translation Dover Edition • 13 books of propositions, based on 5 postulates. 1 Euclid's 5 Postulates 1. A straight line can be drawn from any point to any point. • • A B 2. A finite straight line can be produced continuously in a straight line. • • A B 3. A circle may be described with any center and distance. • 4. All right angles are equal to one another. 2 5. If a straight line falling on two straight lines makes the interior angles on the same side together less than two right angles, then the two straight lines, if produced indefinitely, meet on that side on which the angles are together less than two right angles. � � • � + � < 180∘ • Euclid's Accomplishment: showed that all geometric claims then known follow from these 5 postulates. • Is 5th Postulate necessary? (1st cent.-19th cent.) • Basic strategy: Attempt to show that replacing 5th Postulate with alternative leads to contradiction. 3 • Equivalent to 5th Postulate (Playfair 1795): 5'. Through a given point, exactly one line can be drawn parallel to a given John Playfair (1748-1819) line (that does not contain the point). • Parallel straight lines are straight lines which, being in the same plane and being • Only two logically possible alternatives: produced indefinitely in either direction, do not meet one 5none. Through a given point, no lines can another in either direction. (The Elements: Book I, Def. -
The Celestial Sphere
The Celestial Sphere Useful References: • Smart, “Text-Book on Spherical Astronomy” (or similar) • “Astronomical Almanac” and “Astronomical Almanac’s Explanatory Supplement” (always definitive) • Lang, “Astrophysical Formulae” (for quick reference) • Allen “Astrophysical Quantities” (for quick reference) • Karttunen, “Fundamental Astronomy” (e-book version accessible from Penn State at http://www.springerlink.com/content/j5658r/ Numbers to Keep in Mind • 4 π (180 / π)2 = 41,253 deg2 on the sky • ~ 23.5° = obliquity of the ecliptic • 17h 45m, -29° = coordinates of Galactic Center • 12h 51m, +27° = coordinates of North Galactic Pole • 18h, +66°33’ = coordinates of North Ecliptic Pole Spherical Astronomy Geocentrically speaking, the Earth sits inside a celestial sphere containing fixed stars. We are therefore driven towards equations based on spherical coordinates. Rules for Spherical Astronomy • The shortest distance between two points on a sphere is a great circle. • The length of a (great circle) arc is proportional to the angle created by the two radial vectors defining the points. • The great-circle arc length between two points on a sphere is given by cos a = (cos b cos c) + (sin b sin c cos A) where the small letters are angles, and the capital letters are the arcs. (This is the fundamental equation of spherical trigonometry.) • Two other spherical triangle relations which can be derived from the fundamental equation are sin A sinB = and sin a cos B = cos b sin c – sin b cos c cos A sina sinb € Proof of Fundamental Equation • O is -
Appendix a Glossary
BASICS OF RADIO ASTRONOMY Appendix A Glossary Absolute magnitude Apparent magnitude a star would have at a distance of 10 parsecs (32.6 LY). Absorption lines Dark lines superimposed on a continuous electromagnetic spectrum due to absorption of certain frequencies by the medium through which the radiation has passed. AM Amplitude modulation. Imposing a signal on transmitted energy by varying the intensity of the wave. Amplitude The maximum variation in strength of an electromagnetic wave in one wavelength. Ångstrom Unit of length equal to 10-10 m. Sometimes used to measure wavelengths of visible light. Now largely superseded by the nanometer (10-9 m). Aphelion The point in a body’s orbit (Earth’s, for example) around the sun where the orbiting body is farthest from the sun. Apogee The point in a body’s orbit (the moon’s, for example) around Earth where the orbiting body is farthest from Earth. Apparent magnitude Measure of the observed brightness received from a source. Astrometry Technique of precisely measuring any wobble in a star’s position that might be caused by planets orbiting the star and thus exerting a slight gravitational tug on it. Astronomical horizon The hypothetical interface between Earth and sky, as would be seen by the observer if the surrounding terrain were perfectly flat. Astronomical unit Mean Earth-to-sun distance, approximately 150,000,000 km. Atmospheric window Property of Earth’s atmosphere that allows only certain wave- lengths of electromagnetic energy to pass through, absorbing all other wavelengths. AU Abbreviation for astronomical unit. Azimuth In the horizon coordinate system, the horizontal angle from some arbitrary reference direction (north, usually) clockwise to the object circle. -
Paths Between Points on Earth: Great Circles, Geodesics, and Useful Projections
Paths Between Points on Earth: Great Circles, Geodesics, and Useful Projections I. Historical and Common Navigation Methods There are an infinite number of paths between two points on the earth. For navigation purposes there are only a few historically common choices. 1. Sailing a latitude. Prior to a good method of finding longitude at sea, you sailed north or south until you cane to the latitude of your destination then you sailed due east or west until you reached your goal. Of course if you choose the wrong direction, you can get in big trouble. (This happened in 1707 to a British fleet that sunk when it hit rocks. This started the major British program for a longitude method useful at sea.) In this method the route follows the legs of a right triangle on the sphere. Just as in right triangles on the plane, the hypotenuse is always shorter than the sum of the other two sides. This method is very inefficient, but it was all that worked for open ocean sailing before 1770. 2. Rhumb Line A rhumb line is a line of constant bearing or azimuth. This is not the shortest distance on a long trip, but it is very easy to follow. You just have to know the correct azimuth to use to get between two sites, such as New York and London. You can get this from a straight line on a Mercator projection. This is the reason the Mercator projection was invented. On other projections straight lines are not rhumb lines. 3. Great Circle On a spherical earth, a great circle is the shortest distance between two locations. -
Of Rigid Motions) to Make the Simplest Possible Analogies Between Euclidean, Spherical,Toroidal and Hyperbolic Geometry
SPHERICAL, TOROIDAL AND HYPERBOLIC GEOMETRIES MICHAEL D. FRIED, 231 MSTB These notes use groups (of rigid motions) to make the simplest possible analogies between Euclidean, Spherical,Toroidal and hyperbolic geometry. We start with 3- space figures that relate to the unit sphere. With spherical geometry, as we did with Euclidean geometry, we use a group that preserves distances. The approach of these notes uses the geometry of groups to show the relation between various geometries, especially spherical and hyperbolic. It has been in the background of mathematics since Klein’s Erlangen program in the late 1800s. I imagine Poincar´e responded to Klein by producing hyperbolic geometry in the style I’ve done here. Though the group approach of these notes differs philosophically from that of [?], it owes much to his discussion of spherical geometry. I borrowed the picture of a spherical triangle’s area directly from there. I especially liked how Henle has stereographic projection allow the magic multiplication of complex numbers to work for him. While one doesn’t need the rotation group in 3-space to understand spherical geometry, I used it gives a direct analogy between spherical and hyperbolic geometry. It is the comparison of the four types of geometry that is ultimately most inter- esting. A problem from my Problem Sheet has the name World Wallpaper. Map making is a subject that has attracted many. In our day of Landsat photos that cover the whole world in its great spherical presence, the still mysterious relation between maps and the real thing should be an easy subject for the classroom.