 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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 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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 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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 Trigonometric Identities  David Manura
Table of Common Angles, Law of Sines, Law of Cosines, and more.
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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 (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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 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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 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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 Trisection Of An Angle  Jim Loy
A discussion of what can and can't be constructed using compasses (for drawing circles and arcs, and duplicating lengths) and straightedge (without marks on it, for drawing straight line segments).
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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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 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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 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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 Tumblehome Learning
Makers of educational products such as Lost in Tangrams and  through a partnership with TERC, with funding from the National Science Foundation (NSF)  Mixing in Math (MiM) cards, gameboards, and books.
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 TurnOnCCMath.net  Confrey, Jere, et al.
Learning trajectories that unpack the K8 Common Core State Standards (CCSSS) for Mathematics from the standpoint of student learning, and elaborate the underlying scientific research in mathematics education. Click on a hexagon or a trajectory for detailed
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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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 The Tutor House: math  Adrianne Meldrum
Tutoring elementary and middle school students, Meldrum would often "hunt the Internet for tips and helps on teaching concepts to my students. I find great stuff, but I wanted somewhere central that other tutors like me could find them...." Every Wednesday
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 The Tutorials Search Engine
Searchable listings of tutorials on a variety of subjects, including mathematics.
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 Tutoring Unlimited  Roman Chertes
Math assistance for local students in Stamford, CT. Information about the tutor and services offered.
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 TutorIT Math Skill Tutors  Intelligent Micro Systems, Ltd's (DBA Scandura)
Adaptive tutorials that identify what a math student does and does not know  and then provide the information needed by that student to master the skills taught. Packages include basic facts (addition, subtraction, multiplication, division), algorithms
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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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 TutorMatch  TutorMatch.com
A tutoring referral service for educators and students. Professional and skilled tutors offer academic assistance and skills development, geared to the learning styles of their students. Tutoring options include face to face meetings or individualized
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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 Pace  Tutorpace Inc.
Online homework help tutoring. Free math resources include descriptions of and primers for prealgebra, algebra, geometry, trigonometry, statistics, and calculus.
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 TutorTeddy.com
Online tutoring sessions across grades in arithmetic, algebra, statistics, probability, calculus, geometry, and trigonometry. The TutorTeddy.com site also freely offers more than a hundred chalkboard video lectures and worked problems.
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 TutorVista  TutorVista.com
Interactive lessons, worksheets, and homework help for math students grades 312 from this online education company.
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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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 TuvaLabs  Tuvalabs LLC
Common Corealigned math learning units based on "topics, news stories, and significant events occurring in student's life outside school," such as sports and nutrition.
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 TuxBlocks  Thomas Price
Click and drag colorful block representations of constants and coefficients from one side of the equation to the other, step by step, to isolate the variables and solve the algebra problems. Points earned through such diagramdriven, mouseonly algebraic
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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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 Twenty Tosses (TEAMS)  Jeannie Toshima; TEAMS Distance Learning, Los Angeles County Office of Education
Toss a coin twenty times, and share class results. Students predicted how many heads or tails they might get if they toss a coin 20 times; tossed coins 20 times and recorded their results; compared their predictions with the actual results; teachers collected
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 Two Equals One?  Jim Loy
A proof that 2=1, what's not "legal" about it, and a discussion of infinity.
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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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 Two Trains  Math Forum, a Classic Problem from the Ask Dr. Math FAQ
Two trains leave different cities heading toward each other at different speeds. When and where do they meet?
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 Tying Down a Random Walk  Ivars Peterson (MathTrek)
For many men, the ordeal of fashioning a neat tie knot is fading into the distant past. It seems ironic that two physicists have now put necktie knots back on center stage. Thomas M. A. Fink and Yong Mao of the Cavendish Laboratory in Cambridge, England,
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 Typing Math  Math Forum, Ask Dr. Math FAQ
How should I type exponents? What about square roots? Why not use tabs? May I send attachments?
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 UCALC  Daniel Corbier
Windows shareware tools to compute compound interest, convert from miles to kilometers, solve a quadratic equation, plot a 3D surface, or simply add up bills. Features include: Expression Evaluator (evaluates expressions such as "5+4*1013"); Unit Converter;
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 UC Museum of Paleontology  University of California at Berkeley
Online exhibits, education and outreach programs, catalogs and collections, and links to other science and museum sites. Paleontology incorporates many different kinds of data from different fields. Search for type specimen data from the museum's Catalogs
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 UCSB Department of Mathematics Center for Mathematical Inquiry  Regents of the University of California
Developing "inquirybased learning approaches in the teaching of mathematics and a research base that examines teaching and learning through inquirybased practices." See past workshops, course materials for University of California Santa Barbara (UCSB)
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 UK Mirror Service  Joint Information Systems Committee, Higher Education Funding Councils, UK
Formerly HENSA, this national software archive service benefits the higher education and research community in the UK, funded by the Joint Information Systems Committee of the Higher Education Funding Councils. It maintains copies of electronic archives
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 The Ultimate Puzzle Site  van Gassel, Heijmans, van Veldhoven
A site in English and Dutch by three Dutch students. Contents include: Various Basic Puzzles and Riddles (no mathematics); Harder Puzzles and Riddles (no mathematics); Mathematical and Logicdeductional Puzzles with solutions; BrainTeasers; and Complex
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 ULTRALAB  Anglia Polytechnic University, U.K.
A research centre that writes software for learners of all ages and researches all aspects of the use of technology in learning. Reports, papers, and articles; 'old' software and hardware computing archive.
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 Unbreakable Ciphers  Jim Loy
Proving that if the method of encryption is complicated enough, almost any encrypted message can be unbreakable.
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