 Descartes 3  Ministry of Education, Culture, and Sport, Spain
Create interactive math lessons in web page format with this applet, or download any of more than 60 already created applets (ranging from "representing numbers on a straight line" to "tables and algebraic terms," from "geometry and a game of billiards"
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 Descartes' Formula (Geometry and the Imagination)  Conway, Doyle, Gilman, Thurston; The Geometry Center
The angle defect at a vertex of a polygon was defined to be the amount by which the sum of the angles at the corners of the faces at that vertex falls short of and the total angle defect of the polyhedron was defined to be what one got when one added
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 Descartes' Rule of Signs  Interactive Mathematics Miscellany and Puzzles, Alexander Bogomolny
A discussion by Scott Brodie of the basis of the attribution to Descartes of the proposition now known as Descartes' Rule of Signs: The number of positive roots of a polynomial with real coefficients is equal to the number of "changes of sign" in the
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 Description of the Julia sets of the Cauliflower fractal  Frans Faase
Investigation of the Julia sets of the Cauliflower fractal, which is a fractal generated by two linear translations with three parameters. The generated fractal can either be solid, connected, or disconnected. The author shows that two Julia sets consisting
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 Descriptive Geometry  Petr Plavjaník
Software for creating and printing drawings, including conic sections, color fillings in Monge's projection, and axonometry. In English and Czech.
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 Design Ideas  Julie Coghill
A series of articles that discuss quilt design using proportion, asymmetry, and Pythagorean triples.
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 Designing a Sustainable Standardsbased Assessment System  Don Burger; Midcontinent Regional Educational Laboratory (McREL)
Designing and implementing a sustainable standardsbased system that consistently yields high student achievement involves more than setting and measuring academic goals. Changing to a standardsbased system provides an
opportunity to reexamine the
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 Designing Effective Professional Development: Lessons from the Eisenhower Program  U.S. Department of Education
The second report of the National Evaluation of the Eisenhower Professional Development Program, Part B (State and Local Activities), a multiyear evaluation being conducted by the American Institutes for Research (AIR) under a contract with the U.S.
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 Designing Geometric Figures  Tim Fahey
Geometric constructions: instructions for constructing a variety of geometric shapes and patterns. Symbols, basic constructions, basic shapes, and how to design patterns.
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 Design Science  Design Science, Inc.
Math publishing and presentation tools for the web: MathType, the professional version of Equation Editor, for Windows or Mac; WebEQ, for building interactive math web pages; MathFlow, math publishing for the enterprise; and MathPlayer, to display MathML
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 Design Your Future  Math, Science, and Technology for Girls  Autodesk, Inc.
The Design Your Future mission is to provide practical, inspiring, hands
on opportunities for young women to become aware of, explore, and pursue
math, science, and technologybased careers. It provides a number of opportunities, including: a tool
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 Desmos  Desmos Inc
This free online graphing calculator zooms in and out of plots, offers slider bars to explore parameters, switches between Cartesian and polar coordinates, and more. Save sketches, mark points of interest, turn on "projector mode" for thicker, darker
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 Des Trucs et des Maths  Philippe Picart
Sur le nombre pi; le nombre d'or; le Rubik's cube; des ressources à télécharger; et "des trucs de maths divers," comme un JavaScript qui répond à la question "Quel jour de la semaine estu né?" Avec un coins des
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 Determinación Geométrica de los Números Primos y Perfectos  Omar E. Pol
Un breve ensayo en que "se describe la geometría que determina la distribución exacta de los números primos y también de los números perfectos. Se ilustra el texto con diagramas originales; se muestra el modelo principal
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 Detracking America's Schools: The Reform Without Cost?  Brewer, Rees, Argys; Phi Delta Kappan
The practice of grouping school students by level of ability, known as tracking, has long been used in American public schools. In recent years, opponents of tracking have argued that belowaverage students are hindered by being grouped together, while
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 DevApprentice: Software Developer Apprentice  Kent Griffin
An online resource for learning elementary computer programming. Write and execute real programs, including graphics, in your web browser. Includes a programming problem of the week, examples, instructions, a glossary, and the online programming environment.
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 developer.com's collection of math Java applets  EarthWeb, Inc.
A browsable, searchable collection of links, authors, notes, and details about Java applets contributed to developer.com. Software is organized into the categories of basics and children's, fractals, games and puzzles, general, geometry, plotting, graphing,
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 Developing A General 2nd Degree Diophantine Equation x^2 + p = 2^n  Thien Do; Westmoore High School, Oklahoma City, OK
Using methods of congruences, the author shows that if p = 3 there is only one positive solution (1,2), and if p is any other odd prime not congruent to 7 mod 8, there are no solutions. Introduction; Methodology; Conclusions; Further Works; Acknowledgements;
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 Developing Educational Standards for Schools  Charles Hill; Putnam Valley Schools, New York
An annotated list of sites that have educational standards documents prepared by various states and professional organizations. View standards by subject area or U.S. state. There is a list of state education departments, and resource pages on: U.S. government;
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 Developing Function Sense with SAQs  Judah Schwartz
A work in progress, this is an online book on the philosophy of teaching functions in middle and high school algebra. He has come to believe "that approaching algebra through the study of functions using symbolic and graphical representations simultaneously
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 Developing Quality in Mathematics Education  Christof Höger
Download Microsoft documents of short word problems and their solutions, each categorized by age and tested for use in the classroom. Developing Quality in Mathematics Education (DQME) received support from the European Commission. Also available in Danish,
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 De Viribus Quantitatis  The University of Bologna
Luca Pacioli, a Franciscan monk, mathematics tutor, and colleague of Leonardo Da Vinci, wrote this foundational text of modern magic and numerical puzzles between 1496 and 1508. De Viribus Quantitatis (On the Powers of Numbers) contains the first ever
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 Devising channels that nurture ingenuity and creativity in mathematics classes.  Helen Christensen; Loyola College; The Math Forum
Summary of a presentation given at the 1996 Joint Mathematics Meetings in Orlando, Florida. Original projects and individual journals can challenge students who are more linguistically oriented, and who crave expression for their ingenuity and creativity
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 Diario Fractal  Today´s Fractal  Juan Pablo Braña
A site from Buenos Aires, in English and Spanish, with a different fractal art image every day and archived galleries of past images.
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 Dice and Valentine's Day Symmetries (Math Chat)  Frank Morgan; Christian Science Monitor
A dice challenge from S. H. Logue: The six faces of four dice have these numbers on them: A 1 1 5 5 5 5 B 4 4 4 4 4 4 C 3 3 3 3 7 7 D 2 2 2 6 6 6. You and your opponent each choose one die to use throughout the game. Each round you both roll, and the
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 A Dice Game  Doug Ensley, Shippensburg University
In this game, two players roll dice repeatedly taking note of who has the higher roll each time. The original number of dice for each person and the number of rolls are set by the user. At the end, the percentage of wins for each player is displayed.
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 Dictionary of Number Words  Intergalactic Power & Light
A dictionary of English language words, phrases, prefixes, suffixes, and
symbols that describe numbers. Cardinal Numbers, Ordinal Numbers, very large numbers, Noninteger Real Numbers, Numeric Ranges.
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 A Dictionary of Units  Cleave Books
A summary of units of measurement worldwide (current units and a few of historical interest); conversion factors to the SI (Systeme International); an outline of the SI; its basic defining standards and some of its derived units; all the SI prefixes
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 Did You Know? Applications of Statistics  Ian Gordon; University of Melbourne, Australia
Short stories about the application of statistics in different fields: Analysis of Gambling Strategies; Random surgical operations; TV phonein polls; Was it the orange juice?; Sunlight and skin cancer; Firefighters cause damage?!; What was the question
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 DieCast Polyhedra Models  Pedagoguery Software
Sets of small diecast solid aluminum polyhedra, in various colors, available for online purchase.
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 Dien dàn Toán hoc.net
A math site in Vietnamese.
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 A Difference  Darren Kuropatwa
This Winnipeg precalculus teacher's blog serves to "... record and reflect on my personal evolution of how to integrate ... technologies into my teaching." Blog posts dating back March, 2005, include "Wikis As Assessment For Learning Tools" and "Great
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 Differential Equations (calculus@internet  Mathematica)  Christopher A. Barker
Mathematica Track. 1. Basics (Mathematica Overview; The Environment; Arithmetic; Using Variables; Working with Lists; Vectors & Matrices; Algebraic Operations; Functions; Calculus Operations; Graphics). 2. Differential Equations (Creating Slope Fields;
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 Differential Equations  Math Forum
Links to some of the best Internet resources for differential equations: classroom materials, software, Internet projects, and public forums for discussion.
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 Differential Equations (S.O.S. Mathematics)  Dept. of Mathematical Sciences, Univ. of Texas at El Paso
An online course: learning units presented in worksheet format review the most important results, techniques and formulas in college and precollege differential equations. Sections include: Introduction and First Definitions; Modeling via Differential
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 Differential Geometry (Graphics Archive, Special Topics)  The Geometry Center
Using differential calculus to study curves and surfaces in space.
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 Differential Geometry Images  Walter Seaman
Animations of differential geometry topics: images constructed by Seaman using the programs in Modern Differential Geometry of Curves and Surfaces with Mathematica (Second Edition) by Alfred Gray. Topics include: Curves with prescribed curvature and torsion;
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 A Different Kind of Multiplication  David P. Stern
Roman numerals were an improvement on older notation and useful for the abacus, but seemingly impractical for multiplication. Yet a multiplication method was developed, and is described here. The Romans did not understand why it worked, but we now realize
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 Different Ways to Represent Numbers  Chad Lake
Online paper that discusses and illustrates counting in bases other than 10; converting to decimal; the Snake Algorithm (the algorithm, summary of binarytodecimal Snake Algorithm, decimaltobinary Snake, extending the Snake to other bases, and summary
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 Digital Deletions  Pierre Ysewijn
An interactive JavaScript version of Conway's Digital Deletions game, in which numbers in a string are lowered to zero or erased. Users can play with different numbers of digits, different strategy levels, different starters, different sources of digits
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 Digital Generation Unit Conversions  Digital Generation
Choose from 26 different categories of engineering and scientific units. Also available at http://www.webcom.com/legacysy/convert2/convert2.html and http://www.legacysy.com/~legacysy/convert2/convert2.html.
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 Digital Library: Science, Mathematics, Engineering and Technology Education (SMETE)  NEEDS
This site contains a searchable working prototype of a National Science, Mathematics, Engineering, and Technology Education Digital Library; a prototype federated search for the math community and the American Mathematics Metadata Task Force (AMMTF);
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 Digital Library  The Exploratorium, San Francisco
The Exploratorium AtoZ. Archived webcasts, web cams, past exhibitions: stills, movies, sounds, and other experimental items. Online versions of a few of the Exploratorium's interactive exhibits; the Exhibit CrossReference  an experimental database
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 Digital Mathematical Performance  Gadanidis, George; Borba, Marcelo; Hughes, Janette; et al.
Watch video, liveacted dramatic storyboards, and animations of how people "perform" mathematics: Flatland, "Help Me, Fermi," Should Parallel Lines Never Meet," "The Pleasure of Making 10" (linear equations), "The Waiter" (the missing dollar problem),
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 Digital Mathematics Archive  SunSITE.UBC.CA
A digital collection of mathematical sources, with a primary focus on documents from the late 19th century through today. Papers, letters, manuscripts, email messages, Usenetnews postings, computer rendered images and computations, program source code.
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 Digital Promise
Improving the opportunity to learn for all Americans, and accelerating innovation in education, through technology and research. Initiatives include Digital Promise Schools, in partnership with Verizon; the League of Innovative Schools; educator microcredentials,
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 The Digit Connection  Lizzie
A tribute to the number pi through music, poetry, and fiction. (Meet Sailor Pi!) Also includes a brief history of pi with some ways to calculate it, a quote collection, and ways to celebrate the number  even if it's not Pi Day.
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 Digits, Squares, and Cycles  Ivars Peterson (MathTrek)
Fascinating patterns lurk among the digits of whole numbers. Pick a positive integer, such as 57. Square each of the digits, then add the squares together: 5^2 + 7^2 = 25 + 49 = 74. Do the same thing with the digits of 74: 7^2 + 4^2 = 49 + 16 = 65. Keep
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 DIGSTATS  Statistics  Central VA Governor's School for Science and Technology
Pages for descriptive statistics, inferential statistics, and graphical analysis, from the 1997 Central VA Governor's School for Science & Technology. Activities for spreadsheets and the graphing calculator that explore measures of central tendancy
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 DIMACS Research and Education Institute (DREI)  Rutgers University
An institute from the Center for Discrete Mathematics and Theoretical Computer Science which takes the approach that research and education should work handinhand, that collaborations between researchers and educators are formed by understanding each
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