 An Amazing, Space Filling, NonRegular Tetrahedron  Peg Cagle and Joyce Frost, Park City Mathematics Institute
The rhombic dodecahedron derives its name from its twelve ("dodeca") faces, all of which are congruent rhombi, each formed by joining two tetrahedra. In this article, Cagle and Frost explore these related polyhedra, showing how to exploit their space
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 America Counts  U.S. Department of Education
In 1997 President Clinton issued a Presidential Directive to the Department and the National Science Foundation to work together to devise an action strategy for using Federal resources in support of improving student performance in mathematics. The result
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 American Go Association
Learn to play the ancient Chinese board game called Go in Japan, Baduk in Korea, and Weichi in China. Go is said to be 4,000 years old, and is played worldwide. This site lists clubs and resources for beginning and expert players. The AGA provides free
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 American Institute of Mathematics
The American Institute of Mathematics (AIM) "expands the frontiers of mathematical knowledge through focused research projects, sponsored conferences, and the development of an online mathematics library." See, in particular, the nonprofit organization's
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 American Journal Of Mathematics (AJM)  Shiffman, Shokurov, Hida, Zworski, Eds.; The Johns Hopkins University Press
AJM does not specialize, but publishes articles of broad appeal covering the major areas of contemporary mathematics. Subscription information, guidelines for contributors, and copyright information can be found at the site.
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 American Mathematical Society Committee on Education  EMath  Web Site of the AMS
The Committee charge, membership, contact information, annual reports for prior years, and links to education pages on the site are available.
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 American Mathematics Competitions  Dr. Walter E. Mientka, Executive Director
The American Mathematics Competitions (AMC) seek to increase interest in mathematics and to develop problem solving ability through a series of competitions for junior/middle (grades 8 and below) and senior high school students (grades 912). They include
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 American Pi  Lawrence Mark Lesser
Song lyrics by Lawrence Mark Lesser, approximately to the tune of Don McLean's "American Pie." Read a PDF of the Texas Mathematics Teacher article Slices of Pi: Rounding Up Ideas for Celebrating Pi Day, and see Lesser's "mathemusician" page for more lyrics
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 American Regions Math League (ARML)
An annual national mathematics competition. High school students form teams of 15 to represent their city, state, county or school and compete against the best in the from the United States and Canada. The event consists of Team, Power, Individual and
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 American Scholastic Association
Home of the American Scholastic Mathematics Association (ASMA) Annual Math Contest for junior, intermediate, and senior high schools. Read about the contest design and general information; see a list of the year's high performers and their school affiliations;
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 America's Favorite Number (Math Chat)  Frank Morgan, MAA Online
Math Chat invited each reader to send in a number. The most commonly submitted number, with the best explanation of why, wins. Answer: In a tight race between 7 and pi, pi wins by a single vote...
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 The Americas  Mathematics and the Liberal Arts  Todd Hammond
Notes on published articles: a resource for student research projects and for teachers interested in using the history of mathematics in their courses. Many pages focus on ethnomathematics and on the connections between mathematics and other disciplines.
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 AmeriStat  Population Reference Bureau and Social Science Data Analysis Network
Graphical and textual summaries of the demographic characteristics of the U.S. population: marriage and family; population estimates and projections; education, race, and ethnicity; income and poverty; foreignborn population; migration; children; older
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 Amlon Tutors
Private tutoring service based in New York City, covering the NJNYCT area. Math topics covered include: Elementary, Algebra, Geometry, Trigonometry, PreCalculus, Calculus, Sequential I, II, II, Statistics.
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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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 Amortization Calculator  myAmortizationChart.com
Online amortization calculator, with definition, schedules, and links to other financial calculators.
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 Amortization Schedule
JavaScript calculators for figuring out loan amortizations, investment fees, debt payoffs, savings, timesheets, and tips; for simulating investments; and for comparing savings rates and mortgages.
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 Amplify U Learning Centre  Ahmed Harb
Academic tutoring in math and physics, with mentoring, and peer networking, for grades 712.
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 AMS Bookstore  American Mathematical Society
A searchable catalog of over thousands of books, videos, journals, software and gift items from the AMS and participating publishers.
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 amte  Association of Mathematics Teacher Educators, Math Forum
A mailing list for discussions concerning teaching standards and practices at the K16 level. Read and search archived messages up through the list's last activity, in September, 2000.
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 amtnys  Math Forum
The general discussion group of the Association of Mathematics Teachers of New York State. Use this service to discuss items of interest to math educators everywhere. Read and search archived messages; and register to post to the discussions.
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 The Analemma 
Bob Urschel, Valparaiso, IN
The figure8 path that the sun makes in the sky is called the analemma. This site explores the paths of the sun and the earth, with investigations into the effects and the math of their elliptical orbits and earth's tilt, and a summation.
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 Analog Gadgets  Interactive Mathematics Miscellany and Puzzles, Alexander Bogomolny
Java simulations of analog gadgets. Includes an analog device simulation for drawing ellipses, a Peaucellier Linkage simulation, an angle trisection demonstration, a demonstration/essay on cycloids, and applets on geoboards (with a proof of Pick's Theorem)
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 Analysis & Knowledge  Sanford Aranoff
Download data analysis software, such as Patterns, which analyzes and charts trends in stock market using Andrews concepts. See also this former Rutgers University physics professor and current high school educator's thoughts on teaching and help file
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 The Analyst  George Berkeley
A text based on the 1898 edition of the works of George Berkeley, edited by George Sampson, incorporating a small number of changes. Many mathematicians published replies to Berkeley's attack on contemporary mathematical practice in The Analyst. Included
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 The Analytical Engine  John Walker
The mathematician Charles Babbage designed an Analytical Engine, a mechanical precursor to the computer, in the late 1800s. Read historical documents related to the Engine, including Blaise Pascal's account of his mechanical adding machine (in French),
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 Analytic Cycling  Tom Compton
Software that provides technical methods for evaluating and estimating cycling performance and parameters. It makes extensive use of differential equations and advanced numerical methods.
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 Analytic Geometry: Cylindrical Coordinates (Ask Dr. Math FAQ)  Math Forum
A discussion of cylindrical coordinates and their common uses.
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 Analytic Geometry Formulas  Math Forum; Ask Dr. Math FAQ
Analytic geometry (a branch of geometry in which points are represented with respect to a coordinate system, such as cartesian coordinates) formulas for figures in one, two, and three dimensions: points, directions, lines, triangles, polygons, conic sections,
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 Analytic Geometry  Jim Loy
This is a quick introduction to analytic geometry, graphing functions in a coordinate system, that foreshadows the derivative.
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 Analytic Geometry: One Dimension  Math Forum; Ask Dr. Math FAQ
Formulas for analytic geometry figures and concepts in one dimension: points, general quadratic equations, and circles.
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 Analytic Geometry: Polar Coordinates (Ask Dr. Math FAQ)  Math Forum
A discussion of polar coordinates, and formulas for points, directions, translations, rotations, lines, triangles, and conic sections in polar coordinates.
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 Analytic Geometry: Spherical Coordinates (Ask Dr. Math FAQ)  Math Forum
A discussion of spherical coordinates and their common uses.
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 Analytic Geometry: Three Dimensions  Math Forum; Ask Dr. Math FAQ
Formulas for analytic geometry figures and concepts in three dimensions: points, directions, lines, planes, triangles, tetrahedra, general quadratic equations and quadric surfaces, and spheres.
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 Analytic Geometry: Two Dimensions  Math Forum; Ask Dr. Math FAQ
Formulas for analytic geometry figures and concepts in two dimensions: points, directions, lines, triangles, polygons, conic sections, and general quadratic equations.
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 Ancient India's Contribution to Mathematics  Sudheer Birodkar
Algebra and Geometry in Ancient India, where mathematics had its roots in Vedic literature, nearly 4000 years old. Between 1000 B.C. and 1000 A.D. various treatises on mathematics were authored by Indian mathematicians in which
were set forth for the
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 Ancient Mathematics  SunSITE's Vatican Exhibit; Library of Congress
Math history: math and astronomy in the ancient world. Greek Mathematics, Ptolemy's Geography, Greek Astronomy. Scholarship supported science in this world where faith and science were not yet seen as two irreconcilable cultures. Euclid (Elements, Optics);
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 Ancient Writings Revealed!  The Exploratorium
Ancient ideas met modern science at the Exploratorium, San Francisco, CA, on August 4, 2006. Using stateoftheart scientific tools, oncehidden writings by the ancient Greek mathematician Archimedes were uncovered, revealing evidence of science not
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 ... and Math Tutoring  Stuart Raffeld
This oneonone tutoring service meets tutees throughout California's West San Fernando Valley, and also tutors online, overthephone, and by email. Posts in Stu's blog, which date back to February, 2011, have included "Ten Ways to Improve your SAT
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 Andrew M.H. Alexander
JavaScript by Alexander includes "the gear seer," which shows not just bike gear ratios but gear inches and meters development. Input wheel and tire size to see speed at a given cadence. This bicycle drivetrain visualizer further compares different drivetrains,
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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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 Angles of Reflection  John Benson and P. J. Karafiol
A backandforth intergenerational blog on math education, begun in January, 2011, by two Presidential Awardees in Mathematics from the state of Illinois.
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 AngryMath  Daniel R. Collins
Blog by an adjunct math lecturer at Kingsborough Community College who believes that "Math is a battle. It is a battle that feels like it must be fought ...," and for whom "math isn't beautiful or fun, but it is powerful, and that's what we need from
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 Animals & Art  M. Crook
A gallery of fractal images created using Ultra Fractal.
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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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 Anisohedral Tilings Page  John Berglund
Tilings and tessellatings with 2anisohedral and other isohedral tilings. With explanations and a bibliography. Berglund's JavaSketchpad applets include circles in a lattice shape; affine polygons, which extends Napoleon's theorem from a triangle to a
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 Annenberg Institute for School Reform (AISR)  Brown University
The Annenberg Institute develops, shares and acts on knowledge that improves outcomes of schooling in America, especially in urban communities and in schools serving disadvantaged children. Institute Projects: Rethinking Accountability; Building Capacity;
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