 42eXplore  Annette Lamb and Larry Johnson
Web projects that offer definitions, activities, four good starting points, and many more links and resources for thematic topics such as charts and graphs; codes, ciphers and secret messages; fractals, tessellations, geometric shapes, and figures; number
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 7puzzle  Paul Godding
School visits by the UK's "Puzzle Man" feature numberrelated board games, card games, tricky puzzles, and other math activities that involve logic, strategy, and spatial/visual awareness to improve children's mental arithmetic skills and feed their enthusiasm
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 ABCya.com  ABCya.com, L.L.C.
Free educational math games that introduce basic computer skills: Geometry Practice, Addition with Manipulatives, Subtraction Match Game, Math Facts Basketball, Interactive 100 Number Chart, Math Bingo, Place Value ShootOut, Fraction Tiles, Tower of
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 About a Line and a Triangle  Interactive Mathematics Miscellany and Puzzles, Alexander Bogomolny
An interactive page illustrating how the relation between the vertices and the sides of a triangle can be investigated by rotating the triangle.
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 Active Worksheets  David Womersley, Active Maths Limited
Formerly known as the Worksheet Factory, you can create worksheets online for an annual subscription fee: click on the "change" button and watch the numbers, angles, shapes or equations change; click on the "print" button to print a pupil worksheet and
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 Adam Up  Summerfield, James; Kordan, Samuel
Original music, chants, and other oral mnemonics that tell the adventures of Adam Up, who hated maths "... until the day his grandfather gave him a special calculator to summon The Number Crunchers. These strange bearded creatures then sing him catchy
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 The Altitudes  Interactive Mathematics Miscellany and Puzzles, Alexander Bogomolny
A collection of proofs of the concurrency of altitudes in triangles, featuring a Java applet with which one can see the various points, lines, triangles, and circles associated with any given triangle.
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 The Altitude Theorem for Equilateral Triangles  Web Feats Workshop II
Use the applet to intrigue students with a surprising property of equilateral triangles, stimulate their curiosity to wonder why the property is true, then lead them to understand how the property can be proven in an unexpected way. This workshop was
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 A+ Math
A site developed to help elementary school students improve their math skills interactively, offering: educational math games (learn basic operations and geometry by playing MATHO  bingo and math combined; Hidden Picture; and Concentration), Web flash
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 Amby's Math Instruction, Reinforcement, and Learning Activities  Amby DuncanCarr
Stepbystep tutorials, with autoscoring quizzes: order of operations, solving word problems, properties of numbers, prime numbers, prime factorization, greatest common factors (GCF), least common multiples (LCM), simplifying (reducing) fractions, changing
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 AMOF: The Amazing Mathematical Object Factory  Frank Ruskey
Combinatorial objects are everywhere. How many ways are there to make change for $1 using unlimited numbers of coins of all denominations? Each way is a combinatorial object. AMOF is part encyclopedia and part calculator, a teaching tool that generates
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 Andy Norton's Web Page  Dept. of Mathematics Education, Univ. of Georgia
Illustrated essays and explorations of algebra and geometry using various technology, including TI85 calculators, CBL's and computer software such as Geometer's Sketchpad (with sketches to download), Algebra Expressor, and Excel, by a grad student in
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 The Angle Bisectors  Interactive Mathematics Miscellany and Puzzles, Alexander Bogomolny
A discussion of why the anglebisectors of a triangle meet at the incenter of the triangle, in several different ways, involving: cevians, the transitivity property of equality, axes of a 2line, altitudes and orthic triangles, and complex numbers.
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 The Angle Defect of a Polyhedron (Geometry and the Imagination)  Conway, Doyle, Gilman, Thurston; The Geometry Center
The angle defect at a vertex of a polygon is defined to be 2 pi minus the sum of the angles at the corners of the faces at that vertex. What is the angle sum for a polygon (in the plane) with n sides? Determine the total angle defect for each of the 5
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 Angles and angle terms  Mark Motyka, Math League Multimedia
Definitions and illustrations: What is an angle?; Degrees: measuring angles; Acute angles; Obtuse angles; Right angles; Complementary angles; Supplementary angles; Vertical angles; Alternate interior angles; Alternate exterior angles; Corresponding angles;
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 Animated Educational Software  FLIX Productions
Shareware for PC platforms, including programs designed to teach children about money, timetelling, shapes, math (counting, addition, subtraction for preK through 1st grade), and multiplication and division (for 1st3rd graders).
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 Animated Proof of the Pythagorean Theorem  Mark D. Meyerson; Mathematics Dept., U.S. Naval Academy
Starting with a right triangle and squares on each side, the middle size square is cut into congruent quadrilaterals (the cuts through the center and parallel to the sides of the biggest square). Then the quadrilaterals are hinged and rotated and shifted
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 Appetizers and Lessons for Math and Reason  Alan Selby
Logic Appetizers to test or or improve reading, writing and thinking skills, with definitions, concepts and proofs in many subjects (Chains of Reason; One or TwoWay Implications; Islands & Divisions of Knowledge; Deception); Advice (How to Study
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 Approximating the area of a unit circle with regular polygons  Lisa Markus; Furman University, Greenville, SC
A Java applet for the area of a circle of radius 1. Enter the number of sides, from 3 to 1000, draw the polygon, and see the corresponding area.
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 Area and perimeter  Mark Motyka, Math League Multimedia
Definitions and illustrations: Area; Area of a square; Area of a rectangle; Area of a parallelogram; Area of a trapezoid; Area of a triangle; Area of a circle; Perimeter; Circumference of a circle.
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 Association of Teachers of Mathematics (ATM)
A U.K.based association that aims to support the teaching and learning of mathematics by encouraging increased understanding and enjoyment of mathematics. It addresses all those concerned with mathematics education in primary schools, secondary schools,
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 Bee Alert  University of Montana
Bees and portable computers can now be used to assess environmental hazards through the development of electronic hives, toxicological models, extensive databases, and patternrecognizing software that help assess risks posed by metals, radiation, carcinogenic
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 BitArt  Robert J. Krawczyk
Illustrated introductions to spirolaterals and strange attractors. See a selfrunning demonstration of a variety of spirolaterals, or generate one of your own and see all the reversals. The link of current exhibits lists installations showing strange
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 Bob's Pages  Bob Allanson
A collection of geometry applets. Generate and modify polyhedra, investigate the Mandelbrot and Julia sets, or experiment with Pappus's arbelos, the porisms of Poncelet and Steiner, and a logarithmic spiral.
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 Brahmagupta's Formula  Jim Wilson, Dept. of Mathematics Education, Univ. of Georgia
Problem: Develop a proof for Brahmagupta's Formula, which provides the area A of a cyclic quadrilateral (i.e., a simple quadrilateral inscribed in a circle) with sides of length a, b, c, and d as A = sqrt((sa)(sb)(sc)(sd)) where s is the semiperimeter
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 Breaking Chocolate Bars  Cut the Knot!, Alexander Bogomolny
The chocolate bar puzzle has three parameters: two side lengths (m and n) and actual selection of lines along which to break the bar and its parts... An interactive column for MAA Online that uses a Java applet to simulate a puzzle or mathematical problem,
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 Brightest Moon for Thousands of Millennia? (Math Chat)  Frank Morgan, MAA Online
Answer to the challenge: Was there any validity to the claim that the full moon of December 22, 1999 was the brightest that we shall see for millions of years? (Factors that coincided.) New challenge: Eric Brahinsky saw in an article on "New molecule
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 Building Blocks  Doug Clements and Julie Sarama, University at Buffalo, State University of New York
Supplementary and enrichment math materials for young children. Project writings include "Mathematics in the Preschool"; "'Concrete' Manipulatives, Concrete Ideas"; "Mathematics for Young Children"; "Technology and School Change: New Lamps for Old?";
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 CalculateWhat  Colin Fagras
Free online calculators. In addition to covering math topics such as algebra, geometry, and statistics, CalculateWhat crunches numbers on topics financial, scientific, and  under a category called "miscellaneous"  more whimsical and topical in nature.
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 Camping in the Redwoods  Joan Callaway
Math questions based on a visit to see the California redwoods. Part of a sample lesson for the 6th grade "Staying in Shape... Mathematically," one of three ...Ellipsis Middle School Math Summer Practice Programs. An order form for the full set is provided.
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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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 Center for Technology and Teacher Education  Curry School of Education, University of Virginia
An interdisciplinary group that develops materials to prepare teachers to use technology to enhance and extend students' learning of mathematics. This site offers activities using graphing calculators, The Geometer's Sketchpad, Microsoft Excel, the ExploreMath.com
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 Centre for Innovation in Mathematics Teaching  University of Plymouth
A focus for research and curriculum development in mathematics teaching and learning with the unifying aim of enhancing mathematical progress in schools and colleges. The site includes: The Mathematics Enhancement Programme; Resources: worksheets in HTML
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 Christmas With The Polyiamonds Puzzle Family  Jos H. Hindriks
Polyiamonds share their general principles with Pentominoes, except that their basic 'cell' is the sixtydegree triangle instead of the square. The term 'Polyiamonds', derived from the word 'diamond', was introduced in 1961 by T.H. O'Beirne. Hexiamonds,
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 Classroom Projects  TEAMS Distance Learning, Los Angeles County Office of Education (LACOE)
A site for teachers looking for a content area project or contest for the classroom. Join a TEAMS project or browse a list of projects and contests sponsored by other organizations. Extensive list of upcoming, current, ongoing, and completed projects
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 Collaborative Maths Resources  Collaborative Learning Project
Freely downlaod PDFs of "talkforlearning" lesson plans such as "12 and 24 hour Card Sorting" (clock times), "Buy a Ted" (collect all the parts of a teddy bear, which introduces the concepts such as exact amounts and making change), "Factors Four in
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 Concurrency Points in a Triangle  Brakalova, Johnson, Scalzitti, Thornberry; The Geometry Center
An interactive Webbased exploration designed to facilitate the teaching of triangle concurrency, both as an integral part of a geometry curriculum and as enrichment material. These pages can be used by individual students as a computer exploration, as
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 Concurrent Triangles  Jim Wilson
Sketches and scripts exploring various concurrencies in triangles.
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 Congruence Of Triangles  Jim Loy
A short introduction to equivalent side/angle theorems and congruence postulates in triangles.
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 Congruence Of Triangles, Part II  Jim Loy
This article proves that the three "theorems" or "postulates" that are the basis of Euclid's theories about triangle congruence are actually equivalent.
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 Constant Perimeter and Constant Area Rectangles (Connected Geometry)  Daniel Scher; Education Development Center, Inc. (EDC)
Interactive Java animations accompany the article "Theorems in Motion: Using Dynamic Geometry to Gain Fresh Insights" by Daniel Scher in the April 1996 issue of the Mathematics Teacher. The article outlines how dynamic geometry software can be used to
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 Counting Triangles (SMILE)  Mamie P. Scott, Coles School
A lesson for grade 6 designed to teach students to organize, summarize, and record information; and to discover a rule or formula that will find the total number of triangles in a figure. From the Patterns and Logic section of a collection of almost 200
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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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 Cuisenaire Math  ETA/Cuisenaire
From the makers of Cuisenaire Rods: Connecting Cuisenaire Rods, Cuisenaire Roddles (board games and puzzles that emphasize spatial reasoning skills), Cuisenaire Rods for the Overhead, Magnetic Cuisenaire Rods, and other manipulatives. Publications include
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 Daeron's Java  Daeron Meyer
Numerous applets, created by a former technician at the Geometry Center, can be enjoyed here if you have a Java enabled browser. Mathrelated creations include a 3D viewer; Real time function graph; Rotating Red Triangle; Circle Text; and links to other
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 Dave's Math Tables: Areas, Volumes, Surface Areas  David Manura
Formulas for and diagrams of: areas of polygons (square, rectangle, parallelogram, trapezoid, circle, ellipse, triangles); volumes of polyhedra (cube, rectangular prism, irregular prism, cylinder, pyramid, cone, sphere, ellipsoid); surface area (cube,
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 Defining Geometric Formulas (Ask Dr. Math FAQ)  Math Forum
Definitions of two and threedimensional figures in general, and a note on dimensions.
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 Dekov Software
Educational software, a journal of computergenerated Euclidean geometry, and a computergenerated encyclopedia of Euclidean geometry. Current software titles include: Solving Triangles (stepbystep solutions to triangle problems in elementary geometry);
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 Demiregular Tessellations  Totally Tessellated
Color renditions and a real example of a demiregular tessellation. Templates allow you to print renditions of each tessellation suitable for coloring activities.
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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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