 TreeAge Software, Inc.
Producer of decision analysis software. Product information, interactive demos and trial download, FAQ and technical support, ordering, and registration.
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 TREEFROG Mathematical Software  John Moores University, Liverpool, UK
Modular software for Windows, intended to be used along with traditional teaching methods, to provide instant feedback at each stage. It covers basic order of operations; manipulation of fractions; transposition of formulae and the quadratic equation;
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 TREEFROG selfassessment system  Strickland, AlJumeili
An MSDOS and Windows program for checking math skills, based on mathematical rules. A student is presented with an expression (say integral of x cos x d x, or x2+3x+2 = 0) and told to convert it to another equivalent form (function of x + constant, x
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 Triangle: A TwoDimensional Quality Mesh Generator and Delaunay Triangulator  Jonathan Richard Shewchuk
Triangle generates exact Delaunay triangulations, constrained Delaunay triangulations, and quality conforming Delaunay triangulations. The latter can be generated with no small angles, and are thus suitable for finite element analysis. Instructions for
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 Triangle: A TwoDimensional Quality Mesh Generator and Delaunay Triangulator  Jonathan Richard Shewchuk, Carnegie Mellon University
A triangle that generates exact Delaunay triangulations, constrained Delaunay triangulations, and quality conforming Delaunay triangulations. The latter can be generated with no small angles, and are thus suitable for finite element analysis. Created
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 Triangle Calculator  Peter Chrenko
Select SideSideSide (SSS), SideAngleSide (SAS), AngleSideAngle (ASA), or SideSideAngle (SSA) congruence, then enter three known sidelengths or angles, and this JavaScript returns the triangle's remaining measurements. This calculator also uniquely
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 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 Congruence  Math Forum, Ask Dr. Math Common Question
A selection of answers to questions about triangle congruences, such as "Why can't the SSA Theorem be used to prove congruence?" and "When should we use Congruent Parts Congruent Triangles Congruent (CPCTC), and how does it prove anything?"
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 Triangle Formulas (Ask Dr. Math FAQ)  Math Forum
Formulas for finding the area, perimeter, etc. of an equilateral, isosceles, right, or scalene triangle.
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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: 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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 A Trillion Dollars  Jim Loy
Illustrating large numbers: 100, 1,000, and 10,000 vertical lines; imagining a trillion.
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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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