 Triangle: Proof  Michal Wojcik
A proof that the sum of the angles in a triangle is 180 degrees. This page is written in HTML with two graphical images.
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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 Pyramids: Playing Math!  Hollis Easter
A "teachable" on the construction of freestanding pyramids made "by folding a single piece of paper, with only a single piece of tape to hold them together...." This blog post goes on to include photos of a net, diagrams, and "things to investigate":
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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, Circles, And Waves  Kenny Felder
The site provides an overview of trigonometry. The material is merely
a refresher; only useful to beginners in trigonometry when used as supplementary course material in a trigonometry class.
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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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 Triangle with one 90degree Angle  NASA Lewis Learning Technologies Project
A triangle with one 90 degree angle is always: an equilateral triangle; an acute triangle; an obtuse triangle; or, a right triangle? A detailed answer is provided. From NASA's 9th Grade Math Proficiency Test.
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 Triangular Numbers
Triangular and square numbers, presented with numeric, algebraic, and geometric illustrations, proofs, and formulas.
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 triangular prism  Manjit Singh Atwal
Download lessons and worksheets about triangular prisms, including finding surface areas and volumes.
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 Triangulation (SMILE)  Ann M. W. Brandon, Oak Forest High School
A lesson designed to teach students the basics of how to perform and calculate
triangulation. From the Practical and Applied Math section of a collection of almost 200 single concept lessons by the Science and Mathematics Initiative for Learning Enhancement.
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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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 A Tribute to Miro  Kathy Sederquist, Namaste Art Center
Students learn how contemporary artists work by doing a painting in the style of the Catalan artist Joan Miró. The basic lines in drawing, including vertical, horizontal, diagonal, and curved, are reviewed through experimentation.
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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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 Tricks for Learning Math  Math Forum, Teacher2Teacher FAQ
Answers to a frequently asked question: What are some math tricks and mnemonic devices I can use with my students?
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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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 Tricky Tables (MatheMUSEments!)  Ivars Peterson (Math Muse for Kids)
The shape of a billiard table has a lot to do with the types of shots you can make in a game of billiards. Which of the odd tables pictured do you think would be your best bet for hitting another ball? Suppose you have a circular table, or a rectangular
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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 Functions (SMILE)  Lesia Smith, Michael M. Byrne School
A lesson designed to teach students to define and demonstrate the six trigonometric functions; and to facilitate using the three most frequently used trigonometric functions. From the Algebra and Trigonometry section of a collection of almost 200 single
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 Trigonometric Identities  David Manura
Table of Common Angles, Law of Sines, Law of Cosines, and more.
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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 and Calculus Problem of the Week  Math Forum
Trigonometry and calculus problems from a variety of sources, including textbooks, math contests, NCTM books, puzzle books, and reallife situations, designed to reflect different levels of difficulty. From 1998 until 2002, the goal was to challenge students
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 Trigonometry Challenge  ETCAI Products
A program designed to supplement your classroom and textbook instruction in numerical trigonometry. A trial program is available for download. The generic topics can be used with most textbooks. For Windows 95/98/98SE/me/XP/2000/NT4.
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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 Reference Sheets (S.M.A.R.T.)  Math Share Shop
Basic curves. By students at Theodore Roosevelt H.S., Bronx, & Edward R. Murrow High School, Brooklyn.
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 Trigonometry (Seeing is Believing)  De Silva, D'Andreti; ThinkQuest 1997
A trigonometry tutorial, comprising: angles; trigonometric functions; oblique triangles; vectors; polar cordinates; complex numbers; and hyperbolic functions.
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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 Table  Industrial Press
Tables that give corresponding sine, cosine, tangent, secant, cosecant, and cotangent values for angles 0 to 90 degrees.
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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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 Trimathlon
Site centered around a book featuring activities from number theory and geometry beyond the realm of the typical school curriculum. The site features a discussion forum, a sample online game (with others promised), and a periodic puzzler with hint.
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 TriMathlon: A Workout Beyond the School Curriculum  A. K. Peters, Ltd.
Companion site to the book TriMathlon: A Workout Beyond the School
Curriculum, by Judith and Paul Sally. Discuss math, the book, or the site with members of the Trimathlon community; explore the current "Periodic Puzzler"; or play one of the Shockwave
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 Triogram Models  Hansen, Kooperberg, Sardy
An electronic version of a paper that introduces the Triogram method for function estimation using piecewise linear, bivariate splines based on an adaptively constructed triangulation. Java applets are included and a PostScript version of the entire paper
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 Trisecting a Line Segment  Robert Styer
Several ways to trisect a line segment using compass and straightedge.
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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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 Trisecting the Angle  Steven Dutch; University of Wisconsin  Green Bay
Why is trisecting an angle with a straightedge and compass impossible? Discussion includes several other proofs of impossibility (the largest prime number, the square root of 2, repeating patterns in the plane) and some alternate methods of trisection
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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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 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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 True Learning  Jinhee and Joseph Kim, TrueLearning LLC
Early learning curriculum, worksheets and lesson plans. The True Math activities provide an advanced foundation in math for your child with visually intuitive and engaging exercises. Free samples.
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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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 The True Size Of ...  Talmage, James; Maneice, Damon
Putting the Mercator projection into perspective, one place at a time. Search the world for names of countries, provinces, and U.S. states by name, then drag outlines of them around to compare the actual areas of the land masses.
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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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 The Truth About Math Standards and InformationAge Math Reform  Bill Quirk
An antireform site offering a critical analysis of the NCTM Standards and TERC math.
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 The Truth Tree's Math and Logic Board  Bob Scott, Ron Savori
A collection of math and logic problems, from Pascal's Pizza Parlor and Leaning Ladders to The Old Lady and the Eggs and The Rickety Table Disaster. Register to solve these and other problems and compete with other visitors to The Truth Tree.
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