 Sir Roger Penrose  World of Escher
Recreational math is the passion of Sir Roger Penrose, who was recently knighted for his outstanding contributions to mathematics. Penrose is a professor of mathematics at the University of Oxford in England, where he pursues an active interest in recreational
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 Sir William Rowan Hamilton  D.R. Wilkins; School of Mathematics, Trinity College, Dublin
Material relating to Sir William Rowan Hamilton, including his letters and papers describing mathematical optics and conical refraction, dynamics, the theory of algebraic couples (complex numbers), the theory of equations, and quaternions; a memorial
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 SISA: Simple Interactive Statistical Analysis  Daan Uitenbroek
SISA is a collection of procedures for performing simple statistical calculations online, using HTML Forms. SISA's statistical tools include statistical procedures: (sequential probability, ratios, ttest, Fisher exact, two by two table, ordinal tests,
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 A Site For Cyber Eyes  BZLeonard
Fractals, graphics, photos and altered photos, 3D graphics, links, Sherman's Humor Column, and Ginger's Diary (A teenager describes being bombed by the Japanese on December 7, 1941).
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 Sites with Problems Administered by Others  Math Forum
Problems of the week or month: a page of annotated links to weekly/monthly problem challenges and archives hosted at the Math Forum but administered by others, and to problems and archives elsewhere on the Web, colorcoded for the level(s) of the problems
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 Sketches for Cabri Geomètre (v. 1)  L. J. Dickey, University of Waterloo
Cabri Geomètre (the original version of of the program) figures to download (binhexed): Conic Given by Five Points; Ten Sketches of Desargues Theorem; Harmonic Conjugates; The Inverse of a Circle; The Inverse of a Line; The Inverse of a Point;
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 Sketches of Topology  Kenneth Baker
Visualizations, often created with Sketchup, of low dimensional topology. Blog posts, which date back to November, 2007, have included "Twisted Saddles," "Scharlemann cycles," "Long Disks and Lopsided Bigons," "Ko Honda's Octahedral Relation," "Berge
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 Sketch Exchange  Key Curriculum Press
Share Sketchpad activities, tips, questions, and ideas in this online community dedicated to the dynamic geometry software. Browse sketches by grade level, topic, or tags.
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 SketchMad  Nathalie Sinclair
An archived resource, not currently updated: A resource center devoted to using The Geometer's Sketchpad in the classroom. Includes tips, strategies, lesson plans, and sketches for beginning and intermediate Sketchpad teachers, stories from the classroom
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 Sketchpad 3.0 Gallery  Finzer, Jackiw; Key Curriculum Press & The Math Forum
A collection of sketches and scripts that show off new features of version 3 of the Geometer's Sketchpad in categories: Arcs and Architecture; Algebra and Beyond; Physics; Statistics; Curves; and Poincare Disk.
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 Sketchpad Activity Center  Bill Finzer, Key Curriculum Press
Interactive lessons for use with an early version of the Geometer's Sketchpad. Construct a fractal tree using a recursive script; use the Point on Object command to study random phenomena. These lessons have been used in Key Curriculum Press's summer
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 Sketchpad Homework  Math 5337, The Geometry Center
A set of classical geometry problems created to introduce and teach basic commands for using The Geometer's Sketchpad. Created for Math 5337, Technology in the Geometry Classroom, at the Geometry Center, University of Minnesota.
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 SketchUp  Robert Lang
Tutorials, tips, tricks, and more about the 3D modeling software. Lang, a professional woodworker, cabinetmaker and designer who serves Popular Woodworking Magazine as its Executive Editor, uses SketchUp to design woodworking projects, and as the basis
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 Skill in Algebra  Lawrence Spector
An introduction to algebra, with questions that, when moused over, reveal their answers: algebraic expressions, signed numbers, adding and subtracting signed numbers, multiplying and dividing signed numbers, reciprocals and zero, removing grouping symbols,
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 Skills and Competencies Needed to Succeed in Today's Workplace  NCREL: North Central Regional Educational Laboratory; Learning Point Associates
Because the world of work is changing, the U.S. Departments of Labor and Education formed the Secretary's Commission on Achieving Necessary Skills (SCANS) to study the kinds of competencies and skills that workers must have to succeed in today's workplace.
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 Skimming A Century of Calculus  Cut the Knot!, Alexander Bogomolny
A comprehensive effort is under way to modernize instruction in undergraduate mathematics. In the November issue of the FOCUS newsletter, MAA has announced a twoyear $900,000 grant from the NSF to construct the Mathematical Sciences Digital Library (MATHDL).
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 Skydome Unit Plan  Ruth Carver, Margaret Sinclair
A unit suitable for grades 711 with the objectives: to review many different mathematical skills; to work on a unit that connects with the "real world"; to improve reading for information skills. Questions include: What is the lowest price for a seat
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 Skymath National Weather Report Module
An overview of an instruction unit in which students produce a national weather report and a report on their understanding of various weather phenomena. The unit ties together number sense, symbols, and graphics; emphasizes sorting and counting and making
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 Slates, Slide Rules, and Software: Teaching Math in America  Smithsonian National Museum of American History, Behring Center
An exhibit on mathematics teaching devices from the Smithsonian's National Museum of American History, focusing on innovations in mathematics teaching from the blackboard to graphing calculators and computer software.
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 Sliders  Cut the Knot!, Alexander Bogomolny, with Don Greenwell
A variation of the Fifteen puzzle invented by Sam Loyd in the early 1870's: puzzles on graphs, including a proof independent of Wilson's theorem that all Lucky 7 permutations are possible; and variations of Sliders, a Fifteenlike puzzle that can be played
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 The Slide Rule Universe  Sphere Research Corporation
Slide rule information, lessons, archives, links and an online marketplace: buy, bid for, or swap restored classics, new slide boxes still in the box, and low cost first student rules; learn to operate and care for your slide rule, from Hartung's "A
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 Sliding Pi  Ivars Peterson (MathTrek)
"The entrance to the Downsview subway station in Toronto presents visitors with a striking vista. A vast mosaic of square tiles sweeps across a curved wall, inviting viewers to trace its lines and ponder intriguing irregularities
in its color scheme
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 The Sliding Triangle  Paul Kunkel
Investigate ellipses by tracing triangle transformations.
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 Slinky Science  National Engineers Week Committee
Classroom activities include Racing Slinkys, which describes how inertia, gravity, potential energy, kinetic energy, and longitudinal waves are demonstrated when the Slinky "walks" down stairs or an incline; Slinky Waves, which outlines how Slinkys exhibit
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 Sloan Digital Sky Survey
The astronomical surveys of the Sloan Digital Sky Survey (SDSS) have "obtained deep, multicolor images covering more than a quarter of the sky and created 3dimensional maps containing more than 930,000 galaxies and more than 120,000 quasars." SDSS's
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 Slocum Puzzles  Jerry Slocum
Puzzle collector and author's site. Features puzzle descriptions, shop, descriptions of books written by Slocum and collaborators, and a history of Slocum's famous Puzzle Parties.
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 Slopes and Ski Trails (Why Slopes and More Math)  Alan Selby
What is calculus? If you have ever seen or gone skiing or just walking over hills then you know about slopes and you have met or felt basic ideas in calculus. Calculus in the first instance is the subject of slope computation and interpretation, and the
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 Slope, SlopeIntercept, Standard Form  Math Forum, Ask Dr. Math Common Question
A selection of answers to questions about the slope of a line, and about the slopeintercept and standard forms of the equation of a line, such as "Why are the slopes of perpendicular lines negative reciprocals?" and "How would I draw the line y = (2/3)x
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 Small Group Interactions (Learning and Mathematics)  Susan Bobbitt Nolen; Math Forum
In this 1991 article, "Smallgroup interactions as a source of learning opportunities in secondgrade mathematics," Yackel, Cobb, and Wood, of Purdue University Calumet, Vanderbilt University, and Purdue University, respectively, describe an experiment
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 A Small Puzzle  Joe Fields
The site offers a visual proof that the sum of the first n consecutive odd numbers is n^2, the "L"decomposition.
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 SMARTBoard MiniMovies  Jamie Tubbs
Enhance your SMARTBoard Notebook presentations with these minimovies, which are simple Flash animations. Minimovie topics include: Alphabet Geometry (angles, similar figures, symmetry, transformations, tessellations), Everything Geometry (geometry basics,
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 SmartBoardWiki  Tangient LLC and wiki participants
SmartBoardWiki is a venue where teachers can read, discuss, and increase their experience with SmartBoard technology. Sections include: Hardware FAQs, PD Materials, SMART Use Checklist, Lesson Creation, Advanced Integration, Teacher Notebook Lessons,
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 SMART Catalog  Science and Math Advancement and Resources for Teachers (SMART)
A searchable list of professional development and resource providers for mathematics, science, and technology, organized alphabetically or according to the California Math and Science Frameworks. Articles spotlight professional challenges and successes.
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 Smartkiddies Mathematics  Andy Hobeika
Free interactive lessons, number challenge exercises, worksheets  and visual reporting for instant feedback. To begin, select a year (one through seven, corresponding to Australia's curriculum), then a module, ranging from whole number to position &
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 SMART: Science and Mathematics Advancement and Resources for Teachers  Los Angeles Educational Partnership
A program designed to help teachers in Los Angeles County (California, USA) develop their professional teaching skills and content knowledge. Links for Teachers, Students, Businesses and Institutions, Parents, and Community Members. Includes the SMART
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 Smart Systems Software  Korey Mateer
Smart Systems Software provides freeware for research and development in the field of mathematics. BigGoo Numerical Library, SmartData Data Dictionary, Smart Systems Library, and The Magic Matrix.
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 Só Matemática  Só Matemática
Material para ensino fundamental, médio e superior, além de provas online, biografias de matemáticos, trabalhos de alunos, um acervo de softwares matemáticos, artigos, jogos, curiosidades, histórias, fóruns de
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 SMILE Program Mathematics Index  Science and Mathematics Initiatives for Learning Enhancement
Over 200 singleconcept lesson plans in the following categories: Geometry and Measurement, Patterns and Logic, Probability and Statistics, Recreational and Creative Math, Practical and Applied Math, Arithmetic, Graphs and Visuals, Algebra and Trigonometry,
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 Smithsonian Institution
An independent trust instrumentality of the United States holding some 140 million artifacts and specimens in its trust for "the increase and diffusion of knowledge," and a center for research dedicated to public education, national service, and scholarship
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 Smithsonian Institution Traveling Exhibition Service (SITES)
"The Smithsonian in your state." Each year, millions of people in more than 250 venues beyond Washington, D.C. visit SITES exhibitions on view in local museums, libraries, science centers, historical societies, aquariums, community centers, and schools.
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 Smith's Stuff: Resources  Mark Smith
Mark Smith shares resources that he has created as a high school teacher: games, mnemonics, activities, sketches, and more. Sign up for a free account if you'd like to share activities here as well.
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 snark (Spanish Math Puzzles)  Universidad de Buenos Aires, Math Forum
Contributions are only in Spanish. Una lista de correo electrónico dedicada a la matemática recreativa, los problemas de lógica recreativa, juegos de tablero y problemas sobre ellos, rompecabezas geométricos (poliominós,
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 Snow Activities  The Teel Family
A site that includes snow science (how to study snow crystals) and snow art (cutting sixsided paper snowflakes and a "selfsticking" snowflake).
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 Snow Day Calculator  David Sukhin
Enter a ZIP code and number of school days already canceled there due to inclement weather, and the Snow Day Calculator predicts the probability of an early dismissal or no school the following day. Sukhin originally developed his predictive calculator
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 Snowdays  Popular Front
Make your own snowflakes online: point and click to cut anywhere around or inside the folded piece of virtual paper. Preview the unfolded results in real time; when ready, save your design to the searchable gallery, where you may view and download plans
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 Snowflakes and Stars  Ignacio Dayrit
Graphic images of snowflakes with folding instructions to make from paper.
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 Snowflakes  Kenneth G. Libbrecht
"Your online guide to snowflakes, snow crystals, and other ice phenomena." Snow activities include instructions for using everday objects and dry ice to make your own snowflakes; for using glue to make plastic snowflake replicas ("snowflake fossils")
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 Soap Bubbles  Ron Hipschman; The Exploratorium
Why does a bubble form a sphere? Why not a cube, tetrahedron, or other geometrical figure? This site from San Francisco's Exploratorium provides information on the shape of bubbles and what happens when bubbles meet, with formulas for longlife bubble
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 Soap Film Models (SMILE)  Joan Pintozzi, Curie Metro. High School
A lesson designed to encourage students to conjecture, introducing the concept of minimum path and minimum surface area and practicing measurement of line segments and angles. From the Geometry and Measurement section of a collection of almost 200 single
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 Soap Films and Grid Walks  Ivars Peterson (MathLand)
A simple, physical demonstration of a mathematical truth can produce a lasting impression  one that inspires new questions and speculations. For Christopher C. Chang, a student at Henry M. Gunn Senior High School in Palo Alto, Calif., and one of 40 finalists
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