 Cracking Kepler's spherepacking problem  Ivars Peterson; Science News Online
The familiar piles of neatly stacked oranges at a supermarket represent a practical solution to the problem of packing spheres as tightly as possible. Thomas C. Hales proved that no other arrangement of identical spheres fills space more efficiently,
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 Cracking the Myth of Ball Control  Ivars Peterson (MathLand)
Ball control has become common practice in a number of sports. In basketball, for example, coaches often urge their teams to slow down a game at certain times or to control its tempo. In professional football, "time of possession" has become a statistic
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 Crackpot Index  John Baez
A fun site which outlines how you can tell if a new theory is really from a "crackpot."
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 Crafty Puzzles  James Cole, The Crafty Puzzles Company
A U.K. establishment selling wooden puzzles of all sorts: jigsaw puzzles, puzzle boxes, brain teasers, models, and functional pieces.
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 A Crash Course in Symbolic Logic  D.J. Brasier; Math Forum, Ask Dr. Math FAQ
Is symbolic logic so hard that some people will just never be able to get it? In a gentle introduction to the notation and rules of derivation used in symbolic logic, Dr. Achilles shows why the answer to that question is 'No'.
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 Crashing Waves, Awesome Explosions, Turbulent Smoke and Beyond: Applied Mathematics and Scientific Computing in the Visual Effects Industry [PDF document]  Aleka McAdams, Stanley Osher, and Joseph Teran
The May 2010 issue of the Notices of the American Mathematical Society includes a PDF article (1.3M) entitled "Crashing Waves, Awesome Explosions, Turbulent Smoke, and Beyond: Applied Mathematics and Scientific Computing in the Visual Effects Industry."
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 Crazy Math Teacher Lady  Lisa Bejarano
A high school math teacher in Colorado, Bejarano began blogging after "an awesome 3 day experience at NCTM Denver." Original classroom materials by herself and her students regularly enrich her posts, which date back to that April, 2013 annual meeting
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 CRC Press LLC
A scientific and technical publisher of books, journals, regulatory newsletters, and environmental seminars. A searchable online catalog may also be browsed by topic, among others Engineering, Computer Science, and Math & Statistics.
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 Create 2D and 3D gnuplot Graphs
Input a function, vary parameters, plot 2D, 3D Surface, or 3D Contour, vary range displayed, and plot multiple functions at once. With help on various features, and links to graphing animated plots and varying the parameters. Part of the Shodor Educational
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 Create a Graph  National Center for Education Statistics (NCES)
Create your own graphs online: bar graphs, line graphs, area graphs, pie charts, or XY graphs (line, bubble, or scatter plots from Cartesian coordinates). Enter your own data, choose your own labels, preview your work, then print or save your graphs.
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 Creating NCubes  Dennis Clark
Web and PowerPoint files for learning how to make tesseracts, draw nspace cubes, and chase snakes, or certain closed paths (loops), in nspace cubes. Also, download Ncubes.exe, a Visual Basic program to draw Ncubes.
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 Creative Geometry  Cathleen V. Sanders
Teachers and students will find creative and interesting "handson" projects for most topics in the geometry curriculum. Each project is designed to help students understand, remember, and find value in the concepts of geometry. The pages are organized
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 Creative Java Puzzles  J. L. Read, Enchanted Mind
Games "good for exercising both sides of the brain." Knight's Tour: pass all the squares of the board with the knight, making only legal moves. Peg Solitaire: Remove all the pegs in the least amount of time, finishing with only one peg in the target hole.
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 Creative Problem Solving  Rob Eastaway
Eastaway's "portfolio" of interests includes short descriptions of his school talks, newspaper articles, and books he has authored or coauthored, such as Maths for Mums and Dads, The Hidden Mathematics of Sport, How to Remember Almost Everything, Ever,
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 Crewton Ramone's Blog of Math  Crewton Ramone
Ramone's blog, which dates back to July, 2009, has included posts  many with video  such as "Fractions Despite SPED," "Why Invert and Multiply," "4 Year Old Math Enrichment," "Fractions and Addends," "Fractions and Autism Do in Fact Mix," and "Fraction
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 Critical Evaluation Information  Kathy Schrock's Guide for Educators, Discovery School
With the advent of the World Wide Web and the huge amount of information it contains, students need to be able to evaluate a Web page for authenticity, applicability, authorship, bias, and usability. To help teachers get students started with this process,
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 Critical Issues in Mathematics (NCREL)  Pathways to School Improvement
Articles from the North Central Regional Educational Laboratory (NCREL). The Significance of the NCTM Standards; Ensuring Equity and Excellence in Mathematics; Locating, Using, and Integrating InternetBased Mathematics Materials; Providing HandsOn,
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 Critical Thinking Books and Software
Critical thinking books and software for home and classroom for use in mathematics, science, language arts, social studies, and more. Search for Content Area Mathematics from the classroom catalog or the home catalog.
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 Critical Thinking Puzzles  Eldhose
Puzzles, logical thinking riddles, word problems in blog format. Comment with your solution and read others' workings.
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 Critic of Technology in Schools Faces Tough Audience  Pamela Mendels
From the New York Times column on Education, an April 1998 report on public opinion of the views of Todd Oppenheimer (author of "The Computer Delusion", which apperared in the Atlantic Monthly magazine), from a public meeting concerning technology in
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 CROC'Sciences: le net.magazine de la pédagogie des sciences  P. Lambert
Un mensuel faisant le tour des sites scientifiques d'intérêt
pédagogique, soit pour la construction d'un cours, soit pour les
élèves euxmêmes. Chaque numéro comporte 6
catégories: Mathématiques,
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 Crop circles: Theorems in wheat fields  Ivars Peterson  Science News Online
Patterns of circles and triangles surreptitiously flattened into the crops of southern England reveal the perpetrators' sophisticated knowledge of Euclidean geometry.
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 CrossAge Tutoring  Marah Fortson; Math Forum
An annotated bibliography: articles to help teachers deal with a classroom of learners with different abilities, different strengths and weaknesses, who are at different levels academically, behaviorally, and socially. The task of the teacher is a challenge,
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 Cross Number Puzzles  Rainer Typke
Cross number puzzles to solve online; log in to create your own. Also known as crossfigure, figure logic, or numberlock puzzles, cross number puzzles require numbers instead of words to complete a crosswordlike grid.
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 Crossroads in Mathematics: Standards for Introductory College Mathematics Before Calculus  American Mathematical Association of TwoYear Colleges (AMATYC)
A searchable book on the Web that addresses the need to establish standards for the mathematics programs that bridge the gap between high school mathematics and college calculus. It also aims to satisfy the needs of students who do not plan to study calculus.
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 CRUX Mathematicorum with Mathematical Mayhem  Canadian Mathematical Society
The Digital Supplement to the Canadian Mathematical Society's Problem Solving Journal, for those who practice or teach mathematics. Published eight times per year, the materials at this site are available to all subscribers of CRUX; a sample issue is
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 Cryptarithmetic Puzzle Solver  Naoyuki Tamura
Enter a cryptarithm or select an example, such as SEND + MORE = MONEY. Also, puzzle generators based on themes such as color names, fruits, vegetables, and numeral words in English, French, German, Spanish, and Italian.
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 Cryptarithms  Interactive Mathematics Miscellany and Puzzles, Alexander Bogomolny
Cryptarithms are brain teasers obtained when digits in numerical calculations have been replaced by letters. Customarily, distinct letters stand for different digits. Another term, Alphametics, denotes cryptarithms in which letters form meaningful words,
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 Cryptarithms Online  Jorge Soares
Mathematical puzzles in which the digits are replaced by letters of the alphabet or other symbols. Brainteasers by the author; cryptarithms from the journal Sphinx; a primer; books on cryptarithms, and links to relevant sites on the Web.
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 The Crypto Drop Box of the American Cryptogram Association  Jerry Metzger
The American Cryptogram Association (ACA) is a nonprofit volunteer organization devoted to disseminating cryptographic knowledge. Members make up and solve their own creations strictly for the fun of it. Every two months, the ACA journal, The Cryptogram,
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 A Cryptographic Compendium  John Savard
A book about cryptography with information about a large number of cipher systems and a limited coverage of cryptanalysis. It is mostly concerned with the various kinds of ciphers people have used and only mentions a few things about breaking ciphers.
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 Cryptography AZ  SSH Communications Security
An introduction to the basics of cryptography: Basic Terminology; Basic Cryptographic Algorithms; Digital Signatures; Cryptographic Hash Functions; Cryptographic Random Number Generators; Strength of Cryptographic Algorithms; Cryptanalysis and Attacks
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 CrystalMaker
A Macintosh program to display and manipulate all kinds of crystal structures. Using the free companion program, CrystalDiffract, CrystalMaker files can be used to generate xray and neutron powder diffraction patterns. Main features: In "PhotoColour"
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 CS Bits & Bytes  The National Science Foundation
CS Bits & Bytes highlights innovative computer science research, often at the intersection with other disciplines, and includes profiles of the individuals in the field, links for further exploration, and interactive activities. Past issues of the
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 C++ Simulator of a Turing Machine  Alex Vinokur
A program that simulates the deterministic and nondeterministic multitape Turing Machine. The following demo Turing machines are demonstrated with using the C++ Simulator: an addition program deterministic, 1 tape), an addition program with marker (deterministic,
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 CSMC: Center for the Study of Mathematics Curriculum
An NSFfunded project serving the K12 educational community by focusing scholarly inquiry and professional development around issues of mathematics curriculum. Major areas of work include understanding the influence and potential of mathematics curriculum
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 C.T.J. Dodson  Christopher Dodson
Dodson provides notes and Maple or Mathematica packages for many different mathematics courses, including algebra and precalculus, calculus, differential equations, using computers for mathematics and statistics, and an introductory course on curves,
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 The CTK Exchange  Interactive Math Miscellany and Puzzles, Alexander Bogomolny
A page devoted to questions and answers concerning Bogomolny's pages and math in general. Postings are approved by Bogomolny, and usually answered by him, although they may be answered by the general public as well. Posting topics vary all the way from
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 CTK Math Games for Kids  Interactive Math Miscellany and Puzzles, Alexander Bogomolny
This site presents a collection of Javabased interactive games and puzzles with mathematical contents and a few practice exercises disguised as games. Alexander Bogomolny, the site's author, writes, "There are a few games whose purpose is to allow for
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 Cube Roll  Cary and Michael Huang
Use the arrow keys to steer a cube along a path of squares towards a final square. Each successive level poses new restrictions based on which faces of the block can or cannot roll onto the square path, making a game out spatial thinking of polyhedral
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 Cubes of Perfection  Ivars Peterson (MathTrek)
...Six is the smallest perfect number. Twentyeight comes next. Its proper divisors are 1, 2, 4, 7, and 14, and the sum of those divisors is 28. Incidentally, if the sum works out to be less than the number itself, the number is said to be defective
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 Cubeworld  Hank Gross
Cubeworld: an adventure in solid geometry. This book, with 21 illustrations by the author, is in the tradition of Edwin Abbott's classic Flatland and explores what might happen if the Earth were transformed into a cube. Gravity is different, rain falls
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 Cubic and Quartic Equations  Math Forum, Ask Dr. Math FAQ
General solutions to cubic and quartic polynomial equations.
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 Cubic surfaces  MacTutor Math History Archives
Linked essay on the history of surfaces of order three.
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 CUE (ComputerUsing Educators)  CUE, Inc.
A nonprofit California educational corporation that supports an active membership of more than 10,000 professionals from within and outside California, in schools, community colleges, colleges, universities, related institutions, and related fields.
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 CueThink
Makers of social, collaborative, interactive learning environments such as CueThink, a peertopeer iPad application for grades K12.
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 Cuisenaire Rods and Math (SMILE)  Linda Easter, Dewitt Clinton Elementary School
A lesson designed to familiarize students with the history, development and philosophy of Cuisenaire Rods; to teach them to find the least common multiple of several given numbers using Cuisenaire rods; and to reinforce previously taught math skills by
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 Culturally Situated Design Tools: Teaching Math through Culture  Ron Eglash
Java for creating your own Mangbetu design, cornrow curves, graffiti, bead looms, SimShoBan, Yupik star navigator, Yupik parka patterns, PreColumbian pyramids, and rhythm wheels  and learning the mathematics behind them. Organized into African, African
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 CUNY Games Network  CUNY Academic Commons
Blog about the pedagogical uses of both digital and nondigital math games, how they improve student success, and how they encourage research and scholarship in the developing field of gamesbased learning. Posts, which date back to July, 2011, have included
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 Curmudgeon
Blog by a veteran math teacher in Vermont who "believes that math should be taught, not collaboratively explored; algebra and geometry are better than a vague course of Integrated Math; spiraling doesn't work nearly as well as learning it properly the
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