 Cantor's Theorem  Math Academy Online/Platonic Realms
An article describing Cantor's diagonal argument, which proved that infinity comes in many different sizes.
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 Can You Crack the Enigma Code?  Richard Belfield
The official website accompanying Belfield's book, Can You Crack the Enigma Code? "As part of the book, Richard invited a team of experts from the Information Security Group at Royal Holloway, University of London, to create a challenging collection of
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 Captain Astounding's Nightclub  Dan Welchman
A series of books set in a nightclub, the first of which discusses the practical applications of raising a number to the second, third, fourth and fifth powers. Other topics forthcoming, including "The Probability." The books concentrate on the real meaning
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 Car Budget Activity  Lawrence Klepinger
A handout from The Internet TESL Journal, Vol. III, No. 7, July 1997 (English as a second language). The activity can easily be adapted for different countries and is designed to show the importance of good budgeting and basic common sense when planning
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 Card Colm  Colm Mulcahy
This blog "explores mathematical card principles and effects for fun." Inspired by Martin Gardner and his seminal Mathematics, Magic and Mystery, Mulcahy has posted since August, 2011: "A Call For A New Shuffle Principle (Need Rot Sextet?)," "Splitting
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 Card Games  John McLeod
Rules and information, including probabilities, about card and tile games. Indices by alphabetical order, classified by mechanism and by objective (including a list of children's games), arranged by country and the types of cards. Also, commercial, solitaire,
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 Career Information (SIAM)  Society for Industrial and Applied Mathematics
Examples of questions addressed by applied mathematics  whether genetic engineering, designer drugs, diesel engines, digital TV, financial markets, paper mills, electric power, insurance rates, inflation statistics, computer chips, compact disks, credit
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 Career Profiles 
AMSMAASIAM Mathematical Sciences Career Information Project
Mathematicians at work: practical answers to the question, Why should I study math? More than 40 short essays written by math majors around the country about the types of work they are doing after having received their undergraduate or graduate degrees.
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 C.a.R. Geometry Program  Rene Grothmann
A dynamic geometry program that simulates constructions with a ruler and compass (Compasses and Ruler). C.a.R. runs on Java as a local application, with Java Web Start, or as an applet in browsers. The free and open source program includes documentation
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 Carl Bialik
Author of "The Numbers Guy," a weekly column on "how numbers are used and misused in the news, business and politics," for the Wall Street Journal Online. Read past columns, such as "Putting a Number on Happiness," "Lightning Stats Are Partly Cloudy,"
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 Carlo Emilio Bonferroni  Michael Dewey, University of Nottingham
A brief description of Bonferroni's life and works, including Bonferroni's inequalities and his interest in algebraic means. With bibliographies.
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 Carlson's Fractal Gallery  Paul Carlson
Fractal images in the following categories: 3D Phoenix Spirals; Atan Method (produced by a variety of methods, mostly transcendental functions); 3D Stalks (produced by a variation on a method by Clifford Pickover); Bubbles (standard Mandelbrot); Pokorny
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 Carl's Teaching Blog  Carl Oliver
Blog by a New York City transfer school teacher "documenting the steps I take, and the progress I make, towards becoming the best teacher I can be." Posts, which date back to April, 2014, have included previews of Oliver's lessons for the week and "Carl's
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 Carnegie Foundation for the Advancement of Teaching
An independent policy and research center improving teaching and learning. See in particular Quantway® and Statway®, the foundation's developmental math pathways for community college.
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 Carnegie Learning
A suite of Cognitive Tutors for Algebra I, Geometry, Algebra II and College Algebra. Each course combines computers and paperbased components with professional development, assisting students while ensuring an important role for the teacher. These products
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 Carolina Science and Math Catalogs  Carolina Biological Supply Company
Teachers may request a free catalog with supplies for the math and science classroom. "Carolina Mathematics" includes math teaching supplies, books and workbooks, calculators, posters, tools, and gifts. Features some multicultural materials.
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 Carousel Math  Web Feats Workshop II
Carousels are as reliant on the laws of motion as roller coasters. Let's take a ride on the new Bear Mountain Carousel at Bear Mountain State Park in New York. After enjoying the ride, take the data that has been collected and use the applet to explore
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 Carousel Numbers. A Leadin to Number Theory  Gary Klatt; Univ. of Wisconsin  Whitewater; The Math Forum
A connected series of four problems in elementary number theory that are ideal for discovery learning at several levels. Each problem generates interesting questions and conjectures, and their surprising connections add interest and allow each to shed
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 The Carpets Theorem  Interactive Mathematics Miscellany and Puzzles, Alexander Bogomolny
An intuitively obvious fact that the area of a carpet is equal to the area
of the floor beneath admits several reformulations and nontrivial
consequences, some of which are discussed and dynamically illustrated at
the site.
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 CARROLLIA  Mensa España  CarrollSIG
El órgano de comunicación del CARROLLSIG de Mensa España, que se dedica a las matemáticas recreativas, la lingüística, la literatura experimental, la lógica, la ciencia, y todo aquello que hubiera gustado
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 Carroll's Paradox  Math Academy Online/Platonic Realms
An online encyclopedia article on Lewis Carroll's paradox, in Charles Dodgson's Alice in Wonderland.
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 CARTESIO  Camillo Trevisan
An educational computer graphics program for Windows and Macintosh, providing an understanding of the geometric configuration of projections (for example, the positions of the projection plane and viewpoint relative to the Cartesian axes).
All projection
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 Cartesio  Camillo Trevisan
CARTESIO is an educational computer graphics freeware program for high school and college students exploring and analyzing geometric projections and CAD (computer aided design) principles. Site is in Italian and English, with links to the author's homepage
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 The Case Against Block Scheduling  Jeff Lindsay
An analysis and opinions. Sections include: Nature of the Problem, reviews of case studies (including Bateson's Canadian studies), Advantages of Block Scheduling, Suggestions for Improved Use of Time, Comments From Around the Country, Questions to Ask
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 Case Studies Index  SyllabusWeb
A case study index from A to Z on technology innovation taking place in high schools, colleges, and universities throughout the world, with current studies and text archives.
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 Casio Classpad 300 Resource Center  Saltire Software
The Casio Classpad 300 is an intuitive pen based calculator with draganddrop mathematics and geometry. ClassPad.org is packed with resources to help both teachers and students access the full power of the ClassPad. It includes many explorations and
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 Casio Education  Casio America, Inc.
Calculators, technology, lesson library, activities and sample questions, and other calculator resources for grades K through college. See also Casio's news and events, testimonials, and customer
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 Casio Kingdom  Sean Tan
CFX9850 games and programs. A game and several programs, including: Sphere (solves where a point is in relation to a sphere, whether it lies outside, inside or on the sphere); Divide (finds the position vector that divides vector AB in the ratio a:b);
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 Casio Solutions  Charlie Watson
For CASIO graphing calculator users: high school level Casio calculator resources, including downloadable programs, student worksheets and activities, calculator comparisions, links to other Casio sites, a listing of print resources for educators, with
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 Casting Out Nines  Math Forum, Ask Dr. Math Common Question
A selection of answers to questions about casting out nines, including proofs of why the method works.
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 CASTLE Software
Computer Assisted Student Tutorial Learning Environment (CASTLE) software for Windows, for high school science, social studies, and mathematics  algebra, geometry (including probability), and trigonometry. Includes a tutorial program for student review,
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 Cast Your Vote! What's Your Opinion On Polling?  Annenberg Media
An exhibit that explores wellknown statistical concepts  random sampling, margin of error, and confidence  through activities where YOU play the pollster. Also included is a wealth of links to Web sites related to statistics. The exhibit is part of
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 CataList: Catalog of LISTSERV Lists  LSoft international, Inc.
From this page you can browse any of the approximately 30,000 public LISTSERV lists on the Internet, search for mailing lists of interest, and get information about LISTSERV host sites. This information is generated automatically from LISTSERV's LISTS
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 Catalog of Isohedral Tilings by Symmetric Polygonal Tiles  Doris Schattschneider
A collection of Sketchpad and JavaSketchpad files supplementing the article
"One Corona is Enough for the Euclidean Plane" by mathematicians Doris
Schattschneider and Nikolai Dolbilin. Tilings of the Euclidean plane by a single polygon are considered,
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 A Catalog of Random Bits  Ivars Peterson (MathLand)
Researchers use random numbers for tackling a wide range of problems, from modeling molecular behavior and sampling opinion to solving certain equations and testing the efficiency of algorithms. Such numbers also play crucial roles in a wide variety of
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 Catalog of the Scientific Community in the 16th and 17th Centuries  Albert Van Helden
A searchable collection of 631 detailed biographies with facts about each individual and his or her contributions to science, compiled by the late Richard S. Westfall; Dept. of History and Philosophy of Science, Indiana University.
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 Catalogue of Algebraic Systems  John Pedersen, W. Edwin Clark; Dept. of Mathematics, University of South Florida
Bilinear algebras/ Algebras / Associative algebras; Boolean algebras; Cylindric algebras; Fields; Groupoids; Groups; Inverse semigroups; Jordan algebras; Kleene algebras; Lattices; Lie algebras; Loops; Modules; Monoids; Nearfields / Nearfields; Nearrings;
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 Cattle of the Sun  Ivars Peterson (MathTrek)
The story goes that Archimedes of Syracuse (287212 B.C.) was annoyed with Apollonius of Perga (262190 B.C.), who had criticized Archimedes' work on the multiplication of large numbers. For revenge, Archimedes devised a fiendish computational problem
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 CAUSEweb  Dennis K. Pearl, Director
The Consortium for the Advancement of Undergraduate Statistics Education (CAUSE) collects, reviews, develops, and disseminates resources for members of the undergraduate statistics education community. Resources include lesson modules for lecturers; computer
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 Cavities of chaos  Ivars Peterson  Science News Online
Sorting out quantum chaos in the microwave lab: The rectangle and the (rounded) stadium have long served as geometric playing fields for theorists studying differences between regular and chaotic motion. They can readily calculate sample trajectories
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 cavmaths  Stephen Cavadino
Blog by a maths teacher and KS5 coordinator. Posts, which date back to July, 2012, often incorporate social media and snapshots of scratch work: "Christmaths Projects," "Engaging with Written Feedback," "Consistency, Humour, Well planned Lessons and
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 CC (Concord Consortium) Library: Papers  Robert F. Tinker
From Robert F. Tinker, Director of the Educational Technology Lab of the Concord Consortium, a nonprofit, research and development organization dedicated to furthering the technology revolution worldwide through innovations in hardware, software, learning
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 CCSSI Mathematics
This blog takes "a critical look at the common core state standards in mathematics." Posts, which date back to April, 2012, have included "The concept of none" and "Does a kindergartner need to know what a hexagon is?"
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 CEISMC (Center for Education Integrating Science, Mathematics and Computing)  Georgia Institute of Technology
CEISMC includes the Virtual Institute, which introduces teachers to technology, connects them to the Internet, encourages collaboration, and provides training and resources; and other programs for students and teachers covering: mentoring; career awareness;
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 The Celestial Image of a Polyhedron (Geometry and the Imagination)  Conway, Doyle, Gilman, Thurston; The Geometry Center
Using the celestial image of a polyhedron to get yet another proof of Descartes' angledefect formula. What pattern is traced out on the celestial sphere when you move a flashlight around on the surface of a cube, keeping its tail as flat as possible
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 Cellular Automata  Carter Bays
Applets for Conways' Game of Life, pentagonal cellular automata, triangular cellular automata, hexagonal cellular automata, threedimensional (3D) cellular automata, and more.
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 Cellular Automata Miscellanea  José Manuel Gómez Soto
Cellular automata theses, reports of summer research, working papers, lectures, and articles, some in Spanish, many by Harold V. McIntosh. Also, download the CAM/PC exerciser CAMEX and a program collection of NXLCAU, the Linear Cellular Automata for NeXTSTEP.
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 CeMaST: Center for Mathematics, Science, and Technology  Dossey, Loepp, Fisher; Illinois State University
A program founded in 1990 to provide a locus of campuswide efforts for research, teacher education, curriculum development, and dissemination efforts as they apply to integration in mathematics, science, and technology education. Further information
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 Census and Statistics Department, Hong Kong Special Administrative Region  Hong Kong SAR Government Information Centre
The statistics collection department of the Hong Kong Government. Key geographic, climate, population, and socioeconomic data, press releases, other publications, and an overview of the department. Frequently requested timeseries are available online
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 Census Challenges (Math Chat)  Frank Morgan; Christian Science Monitor
Gordon Squire notes that planners for the 2000 U.S. Census wonder what to do about missing certain groups of people such as many homeless in New York. Suggestions include statistical random sampling. What approach would you suggest?
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