 Triangle Centers  Clark Kimberling; Dept. of Mathematics, Univ. of Evansville, Evansville, IN
A listing, with description and illustration, of 20thcentury triangle centers (including: Schiffler Point, Exeter Point, Parry Point, congruent isoscelizers point, Yff Center of Congruence, isoperimetric point and equal detour point, AjimaMalfatti Points,
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 Triangle in Square Puzzles  Erich's Puzzle Palace; Erich Friedman
Eight puzzles involving cutting squares into triangles under certain constraints. Answers provided.
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 Triangle Puzzle  Evelyn Sander, Geometry Forum Archives, The Geometry Center
Pick an arbitrary point in the interior of an equilateral triangle. Now go halfway towards one of the three vertices (you get to pick which vertex). Now you are at a new point in the triangle. Again go halfway towards any vertex. Continue this process.
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 Triangles and Simplices (The Geometry Junkyard)  David Eppstein, Theory Group, ICS, UC Irvine
An extensive annotated list of links to material on triangles and their higherdimensional generalizations (simplices), with a particular interest in partitioning regions into triangles, tetrahedra, or higher dimensional simplices, for various applications
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 Triangles in Elliptic Geometry  Thomas Banchoff, The Geometry Center
An examination of some properties of triangles in elliptic geometry, which for this purpose are equivalent to geometry on a hemisphere. The aim is to construct a quadrilateral with two right angles having area equal to that of a given spherical triangle.
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 Tribute to Invariance  Cut the Knot!, Alexander Bogomolny
As a competitive activity, the Squares and Circles game is not very challenging in itself. That is to say, the outcome of the game does not depend on how the game proceeds. The challenge is to come up with this realization and establish its veracity.
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 Triceron Archive: Integral Calculus  Triceron.com
An enviroment for exchanging data, among others, theoretical and practical educational resources on integral calculus. Triceron carries a categorised directory of hyperlinks to www/ftp sites, usenet newsgroups, irc channels, freenet sites, usenet servers
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 Tricki  Gowers, Timothy; Sisask, Olof; and Frolkin, Alex
A wiki "repository of mathematical knowhow" that encompasses techniques ranging from the very general to those that concern particular subareas of mathematics. Browse problemsolving ideas by technique: for finding algorithms and algorithmic proofs,
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 Tricky Crossings  Ivars Peterson (MathLand)
Have you heard the one about an itinerant entertainer traveling with a wolf, a goat, and a basket of cabbages? The showman comes to a river and finds a small boat that holds only himself and one passenger. For obvious reasons, he can't leave the wolf
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 Tricky Dice  Ivars Peterson (MathTrek)
The game involves four specially numbered dice. You let your opponent pick any one of the four dice. You choose one of the remaining three dice. Each player tosses his or her die, and the higher number wins the throw. Amazingly, in a game involving 10
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 Trig According to Euclid  Len Smiley, Deborah Smiley
Four figures proving trigonometric addition and subtraction formulas for cosine and sine. Free of Cartesian coordinates, the proofs are synthetic and use a common, minimal diagram from Euclidean geometry.
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 Trigonometric Functions and Calculus  Waner, Costenoble; Hofstra University
A text on the WWW for liberal arts and business majors. Contents (each with exercises): Modeling with the Sine Function; The Six Trigonometric Functions; Derivatives of Trigonometric Functions; Integrals of Trigonometric Functions.
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 Trigonometric Functions  Larry Gladney, Dept. of Physics, Univ. of Pennsylvania
From the Interactive Textbook of PFP 96. A review of the trigonometric functions, sine, cosine, and tangent, as the most frequently used functions seen in introductory physics.
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 The Trigonometric Functions  MacTutor Math History Archives
Linked essay sketching trigonometry from its beginnings out of the early correspondence between astronomy and mathematics through the 18th century, with 17 references (books/articles).
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 Trigonometric Integrals  David Hart
An HTML version of a Maple worksheet used as an alternative to transparencies in a Calculus class lesson at Indiana University. How do you integrate the trigonometric functions? Includes discussion, formulae, diagrams, and exercises.
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 Trigonometry Formulas  Math Forum; Ask Dr. Math FAQ
Formulas for trig functions, bounds, identities, solving right and oblique triangles and inverse trig functions.
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 Trigonometry (Manipula Math)  International Educational Software (IES Inc.)
More than 20 Java applets designed to demonstrate principles of trigonometry, including sine, cosine, and tangent function boxes; graph of y=sin x, y=cos x,
y=sin ax, y=A sin (Bx+C), and y=sin x + cos x; Fourier series; sin t = a;
cos t=a; sin(A+B);
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 Trigonometry (S.O.S. Mathematics)  Dept. of Mathematical Sciences, Univ. of Texas at El Paso
An online course: learning units presented in worksheet format review the most important results, techniques and formulas in college and precollege trigonometry. Trigonometry: Angle Measures, Trigonometric Functions (magic identity, Addition Formulas,
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 Trigonometry  Technical Tutoring
Site provides an introduction to trigonometry, includes illustrative examples and exercises in basic trigonometry as well as a summary of the important basic trig identities and formulae.
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 Trioker  Triominoes Puzzle  J. Marc Genevey
Le jeu de Trioker a été inventé par Monsieur Odier et étudié par luimême et son compère Mr Roussel dans leur ouvrage Surprenant Triangles. Il est composé de l'ensemble des 24 pièces triangulaires
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 Trisecting an Angle  MacTutor Math History Archives
Linked essay tracing the history of the classical Greek problem of trisecting an
arbitrary angle using for the construction only ruler and compass (which is
impossible)  but, failing that, finding some other method.
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 Triseum
Creators of immersive learning video games such as Variant, which brings abstract calculus ideas to life through thirdperson exploration of, and challenges on, a planet governed by calculus principles. Triseum grew out of the Learning Interactive Visualization
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 Triumph of the Nerds: A History of the Computer  Robert X. Cringely; PBS Online
A companion Web site for the Public Broadcasting System television special hosted by Robert Cringely, "Triumph of the Nerds: The Rise of Accidental Empires." Learn how youthful amateurs, hippies, and selfproclaimed "nerds" accidentally changed the world.
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 TRIUMPHS
TRansforming Instruction in Undergraduate Mathematics via Primary Historical Sources (TRIUMPHS) creates freely downloadable materials for use in the undergraduate mathematics classroom which teaches content based around original mathematical sources such
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 Troublesome Weather Trends  Ivars Peterson (MathTrek)
In the February Bulletin of the American Meteorological Society, Statistician Kevin J. Coakley of the National Institute of Standards and Technology in
Boulder, Colo. argues that ... daily temperatures don’t vary randomly. They generally tend to rise
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 Trouble with WildCard Poker  Ivars Peterson (MathLand)
Poker originated in the Louisiana territory around the year 1800. Ever since, this addictive card game has occupied the time and teased the minds of generations of gamblers. It has also attracted the attention of mathematicians and statisticians. The
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 Truel in the Sun  Ivars Peterson (MathTrek)
Brilliant sunshine bakes a huddled row of ramshackle, weatherbeaten buildings lining a dusty thoroughfare. Two gunfighters slam out of a decrepit saloon and stalk toward their posts at either end of the street. Facing each other, they prepare to draw
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 Truncated Octahedron Blocks  Hop David
A discussion of a threedimensional tessellation that may make a good bridge between the rectangular solid tessellation and the octa/tetrahedral tessellation.
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 TSM4: 'Using the Internet for Mathematics'  Oundle School, Peterborough, UK
A oneday conference for teachers held 11 May 1998 at Oundle School, Peterborough, UK. Technology for Secondary and College Mathematics (TSM) is a teacher training initiative based at Oundle School. Online Workshops: "How to download text and images off
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 TSPBIB (Traveling Salesman Problem)  Pablo Moscato
A comprehensive listing of papers, source code, preprints, technical reports, etc., available on the Internet about the Traveling Salesman Problem (TSP) and some associated problems such as Fractal TSP Instances and VRP Instances, with links to software
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 TS Quasigroups (Catalogue of Algebraic Systems)  John Pedersen, W. Edwin Clark; Dept. of Mathematics, University of South Florida
Definition, examples, and references about TS Quasigroups. Links to related terms in the Catalogue.
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 TTC (Tools of Tensor Calculus)  A. Balfagón, P. Castellví, X. Jaén
A Mathematica package for doing tensor and exterior calculus on differentiable manifolds, of interest to the scientist working on any field where tensor calculus is needed. TTC can also be interesting for teaching purposes. Articles, links, and a tutorial.
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 TtH: a TeX to HTML translator  Ian H. Hutchinson
TtH translates TeX source that uses the Plain macro package, or LaTeX, into a near equivalent in HTML. It supports builtup fractions through HTML tables and mathematical symbols via the common extension tag [font face="symbol"] This enables semantically
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 TTMath  big online calculator  Tomasz Sowa
This big numbers library for C++ programming language performs mathematical operations with unsigned/signed integers and floating point numbers.
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 Turbo Tables Educational Software  AGoGoGadget
Intended to teach multiplication techniques especially useful for products larger than 12x12. Includes teaching module, timed trial, and game for practicing your multiplication skills. Free demo available. Available for Windows XP and Pocket PC platforms.
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 TurkZeka  Yilmaz Ekici, TurkZeka.com
Clever puzzles, posted regularly, with quarterly puzzle competitions open to all with free login. In Turkish, English, and Japanese.
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 Turn of the Screw  Ivars Peterson (MathTrek)
Mathematician Chris Rorres of Drexel University in Philadelphia has taken a close look at Vitruvius's specifications for constructing an Archimedes screw... Recent years have seen a revival of interest in the Archimedes screw, particularly for its proven,
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 Turtle Tracks  Ivars Peterson (MathTrek)
One way to describe a geometric figure is in terms of the path generated by a moving point. Using the computer language LOGO, children can produce a list of commands to govern the motion of a "turtle" and trace out a geometric track on the computer screen.
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 Tutor.com  Tutor.com, Inc.
Onetoone realtime help from professional subject experts and librarians. Students looking for homework help may check if their local library or afterschool center offers free tutor.com tutoring; try tutor.com personal online tutoring free for a week;
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 Tutor For Maths  Vikram Singh
Onetoone math tutoring, consulting, brainstorming, and editing sessions conducted online while on the phone with WhizIQ electronic whiteboard software.
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 Tutorials  Harvey Mudd College Department of Mathematics
Primers for precalculus, single variable calculus, multivariable calculus, linear algebra, and differential equations, each with proofs, examples, and key concepts highlighted, some with Mathematica plots to view in a new browser window: algebra review,
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 The Tutorials Search Engine
Searchable listings of tutorials on a variety of subjects, including mathematics.
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 TutorLinker: The Most Innovative Tutor Network  TutorLinker.com
TutorLinker uses online map system so people who are looking for local tutors can easily find their location and compare with other tutors. All services are currently free.
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 tutOR  Moshe Sniedovich and Angie Byrne
An online Operations Research (OR) tutorial system developing tutorial modules for specific OR topics, generic web tools to facilitate the construction of the OR modules, and research of the WWW technologies pertaining to this project. Modules for investigating
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 TutorNEXT  tutorNEXT, Inc.
Oneonone, individualized tutoring sessions in math and English. An enrichment program in math, and free printable math worksheets, are also available. Full listing of services on the site.
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 Tutor World Online
This online tutoring service sells homework help and SAT preparation packages. The Tutor World Online journal posts free primers in math.
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 Tversky's Legacy Revisited  Keith Devlin (Devlin's Angle)
"Amos Tversky died earlier this year. To mathematicians, the Stanfordbased psychologist is best known for the research he did with his colleague Daniel Kahneman in the early 1970s, into the way people judge probabilities and estimate likely outcomes
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 Twistors  What Are They?  Fedja Hadrovic
Notes briefly introducing the basic definitions of twistor theory, which might provide an "elegant formalism for both general relativity and quantum theory. Roger Penrose was first led to the concept of twistors in his investigation of the structure of
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 The "TwoDimensional Factorial" and a New Solution for the Probability of Completing Sets in Random Sampling  Jeffrey D. Lindsay
In finding a new solution to a classic probability problem, The Collector's Problem, concerning the collection of items in a set, a new and useful recursive function has been found, the "twodimensional factorial." A Web adaptation of J.D. Lindsay, "A
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 The TwoHeaded Quarter by Joseph Ganem  Chartley Publishing, LLC
A companion site to The TwoHeaded Quarter, written by a physicist scrutinizing daytoday financial decisions, such as "How far should you drive to buy cheaper gas?" and "Is money saved when you buy on sale?" and "How far should you drive to save money?"
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