 The RightAngle Triangle Solver  Steve Ayers
Input two sides of a right triangle, or one of its sides and one of its angles, and this site calculates the remaining sidelengths and angles. Also, convert decimals and fractions, and imperial and metric units of measure. Requires JavaScript.
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 Right Brained Math  Brandon Price
"Searching for divergence and creativity in all that mathy stuff." Price teaches algebra, geometry, statistics, and robotics at Austin's Khabele School, an International Baccalaureate (IB) World School. His blog, which dates back to March, 2013, has
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 Right Brain  Tom Biesanz, Mister Numbers
Biesanz offers a system for learning times tables through worksheets and a CD. The site offers sample worksheets as well as videos that give an experience of the visual patterns in numbers.
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 Rings (Catalogue of Algebraic Systems)  John Pedersen, W. Edwin Clark; Dept. of Mathematics, University of South Florida
Definition, examples, and decision problems about rings are provided.
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 Rings with Identity (Catalogue of Algebraic Systems)  John Pedersen, W. Edwin Clark; Dept. of Mathematics, University of South Florida
Definition, examples, and decision problems about Rings with Identity, Rings with 1, and Unital Rings.
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 Rinus Roelofs
Geometric sculpture, animation, structures, and "rhinoceros" (knots) by Roelofs, who exhibited as part of the Escher Centennial celebrations. After studying Applied Mathematics at the Technical University of Enschede (Netherlands), Roelofs earned a degree
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 The Rise of Calculus  MacTutor Math History Archives
Linked essay describing the history of Calculus from the Greeks through Newton and Leibniz, with 28 references (books/articles).
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 RiskLab Toronto
One of an international network of math laboratories in the field of risk
modelling. Originally intended to model financial risk, the field has grown
to encompass a number of other areas. Site provides summaries of the lab's
research (including
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 Rite Item  Jim Preston
Software to download: ANYANGLE (Windows, DOS; a geometry solver that provides a method of finding answers to problems involving triangles, and offers scale views and supplementary data to back up the numerical results); and PARTYDOT (a program for creating
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 Rivendell Educational Archive  Leigh Denault
An educational archive of materials in botany, history, math, science, drama, literature, philosophy, and art. Math resources include mathematician biographies, a fractal image gallery, and a bibliography.
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 River Crossing (Math Exploration Quilt)  Rik Littlefield; Hanford School
You want to cross a river to reach a point exactly opposite where you are currently standing. Explore this problem stepbystep, encountering the following basic ideas: 1) Pythagorean theorem; 2) time = distance / speed; 3) distance = time * speed; 4)
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 Riverdeep  Mathematics  Riverdeep Interactive Learning Limited
Online resources for students, educators, and parents, that build on Riverdeep Interactive Learning's courseware and interactive simulations. Read about or demo Destination Math, a curriculum on CDROM in Basic Mathematics, PreAlgebra, and Algebra I
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 A River Runs through It  Stephen Meehan and Maureen Nolan
A local river is the focus for this yearlong series of integrated mathematics and science units for gifted fourth and fifth grade students. Site includes a summary, scenario, internet reference links, and web pages by and for students. Part of the Handbook
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 RJN's More Digits of Irrational Numbers Page  Nemiroff, Bonnell
All digits accessible here were computed by Robert Nemiroff and Jerry Bonnell. The Digit Warehouse: e, sqrts of 2, 3, 5, 6, 7, 8, 10 to millions of digits.
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 Rlab Computer Language  Ian Searle
An interactive, interpreted scientific programming environment for fast numerical prototyping and program development. With numerical solvers and functions from the Gnu Scientific Library (GSL) and the netlib, rlabplus lets you visualize data using gnuplot,
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 RngPack  Paul Houle
A pseudorandom number generator package for Java. Pseudorandom means that the "random" numbers are generated by a deterministic mathematical process, not by a fundamentally random physical process such as radioactive decay or Johnson noise. RngPack contains
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 Rob Barry's Website
Recent stories by The Wall Street Journal investigative reporter who specializes in computerassisted reporting, which he describes as "the practice of wrestling large sets of data into compelling narratives." Barry's articles have ranged from insider
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 Robbins Algebras are Boolean  William McCune, Automated Deduction Group, Argonne National Laboratory
The Robbins problem  are all Robbins algebras Boolean?  has been solved: Every Robbins algebra is Boolean. This theorem was proved automatically by EQP, a theorem proving program developed at Argonne National Laboratory. Information on the solution;
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 Robert Abbott's Mazes  Robert Abbott
Two very difficult puzzles programmed by Oriel Maxime and based on mazes in Abbott's books: the Sliding Door Maze, and Theseus and the Minotaur. Also a collection of reviews of the books SuperMazes and Mad Mazes, with more puzzles (but nothing interactive),
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 Robert J. Lang Origami  Robert J. Lang
Lang has catalogued and diagrammed over 400 models, combining aspects of the Western school of mathematical origami design with the Eastern emphasis upon line and form. Read about origami mathematics, which mathematically describe the underlying laws
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 Robert Kaplinsky  Glenrock Consulting  Robert Kaplinsky
Lessons consist of "The Challenge(s)," "Question(s) To Ask," "Consider This," and alignments to Common Core State Standards (CCSS): "How Can We Water All Of The Grass?" and "How Much Money Should Dr. Evil Demand?" and "How Did They Make Ms. PacMan?"
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 Roberto Tamassia's Home Page
Home page of a Professor in the Dept. of Computer Science at Brown University. Curriculum Vitae, recent papers, teaching, books (interests include graph drawing, data structures, computational geometry).
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 Robert's Online Applications  Robert Lum
Java applets to assist with financial investments: commissions pricer, derivatives pricer, loan pricer, option pricer, option strategy visualizer, portfolio pricer, quote sheet, stock volatility charts, and tax pricer (1999, 1998, 1997, 1996 or 1995).
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 Robo Compass
"Geometrical constructions made easy": type commands such as "draw segment AB between points A and B" and "construct an arc z with center O and radius which is length of segment y," then watch Robocompass draw the construction onscreen with its animated
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 Robotic Navigation with Constraints  J. A. Sethian
A paper and movie on robotic navigation. Finding the Shortest Path: The equation that describes the arrival time of this expanding front as it depends on the possible speed at any point and direction is the Eikonal equation. The fast marching method is
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 Robotics: Sensing, Thinking, Acting  The Tech Museum of Innovation, San Jose, CA
An exibit designed to introduce the science behind the design and operation of robots. Features four exhibit areas: Universal Robots: History and Workings of Robotics; Machines and Man: Robotics and Ethics in the 21st Century; Robot Art: Four Bay Area
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 RockandRoll Bridge  Ivars Peterson (MathTrek)
Startling scenes of rippling pavement, featured in a classic film that captured the 1940 destruction of the Tacoma Narrows suspension bridge in Washington state, rank among the most dramatic and widely known images in science and engineering. This old
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 Rocket High (SMILE)  Elizabeth Kelly, Pilsen Community Academy
A lesson for grades 78 designed to reinforce students' measurement skills by having them manipulate a launcher to create specific angles, introducing them to the concept of tangents. From the Recreational and Creative Math section of a collection of
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 Rockin' the Standards
Musical recordings by a rock band led by a veteran elementary school teacher who takes the lyrics from common tunes and changes them to help kids remember what they've been taught in school. Each of the fourteen songs on the album "Rockin' the Standards
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 Rocky Mountain Mathematica  Ed Packel, Stan Wagon
Introductory and intermediate workshops on Mathematica for teachers of mathematics and other scientific subjects. Workshops are held in Colorado during early July. The site includes registration information, schedule, and syllabi.
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 Rodney Carr's Home Page  Deakin University, Australia
Books and software on statistics and advanced spreadsheet design. Contact the author for passwords to access downloadable documents and executable Microsoft Excel workbooks such as XLStatistics, for statistical analysis of data; XLGenetics, for illustrating
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 Roger Antonsen
Site of the logician, mathematician, computer scientist, researcher, inventor, lecturer, science communicator, public speaker, and author of Logical Methods: The Art of Thinking Abstractly and Mathematically. Blog posts, which date back to 2013, have
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 Rogue Wave's Math Class Libraries  Rogue Wave Software, Inc.
Math.h++ is a C++ class library for any code that manipulates arrays of numbers. Math.h++ offers vector, matrix, and array classes, statistics classes, FastFourier Transformations, and persistence. Product information, technical discussion, Math.h++
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 The Role of Calculators in Math Education  Heidi Pomerantz, Bert Waits for USI/CPMSA
This PDF article outlines the benefits of calculator use in mathematics classrooms from kindergarten through the university level, describing how calculators, when used appropriately, can be a tool for learning mathematics. The document has six sections:
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 The Role of Examples in Learning Mathematics  Annie and John Selden; Mathematical Association of America
"Examining examples and nonexamples can help students understand definitions.... Is the provision of examples always desirable? Would it perhaps be better to ask undergraduate students to provide their own examples and nonexamples? Would they be able
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 Roles of calculators in the classroom  Pedro Gómez and Bert Waits
The site contains the extended papers of the conferences presented in the Topic Group 18 of the International Congress of Mathematics Education held in Seville in July, 1996. Papers are presented both as web pages and as PDF files.
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 The Roles of Interest and Mathematical Beliefs in Preservice Teachers' Learning to Mentor Online [PDF]  Ray & Renninger
Paper presented as part of a symposium, American Educational Research Association, Chicago, IL. A study of preservice teachers working with the Math Forum's Online Mentoring Guide.
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 Rolf's Calculator  Rolf Howarth
A fully featured JavaScript scientific calculator that includes trig functions and logarithms, factorials, 12 levels of parentheses, logs to base 2, bitwise logical operators, hex, octal, binary and ascii display.
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 Rolling a Die Until Every Face Has Appeared (Math Chat)  Frank Morgan, MAA Online
How many times do you think you need to roll a normal die to be 90% sure that each of the six faces has appeared at least once? Why? Answer: It takes 23 rolls, as Al Zimmerman discovered in a computer experiment rolling 5000 dice until 90% of them had
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 Rolling and Learning® with trisquare dice  Creative Enterprises, Inc.
A book describing math games to be played with 14sided dice, suitable for grades K6 or 8. Order form available on the web.
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 Rolling Dice  Math Forum, Ask Dr. Math Common Question
A selection of answers to questions about rolling dice, cube and octahedral, fair and biased, once and many times.
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 Rolling with Reuleaux  Ivars Peterson (MathLand)
Why is the cover of a manhole round? The usual answer is that a circular lid, unlike a square or hexagonal cover, won't fall through the opening. The circle works because it has a constant width, defined as the distance between a pair of parallel lines
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 Rolocu: the Colour Twist Puzzle  Charles Edge
Use logic and planning to put the pieces into place so that all rows and columns have all the colours in them.
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 A Romance With Numbers  K. Venkatasubramanian
Biographical information and thoughts about Srinivasa Ramanujan, from The Hindu, December 24, 1993.
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 Roman Numeral Conversion  InnoVision Technologies
Enter the Arabic number you want to convert to Roman, as long as it's less than 4000.
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 Roman Numerals 101  Oliver Lawrence
The Romans used only seven letters; the combination of a letter and its position could represent any number. They also used a line above the letter, so the numbering system actually represents our own very closely, with fourteen different symbols. The
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 Roman Numerals and Dates  Paul Lewis
An illustrated introduction to Roman numerals, including Roman dates and calendar conversion, history and uses, a page on The Great 1999 Question, and a quiz. Three conversion tables are provided: Numerical 11449; Numerical 14502100; and Alphabetical
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 Roman numerals and decimals (Classics log)  John Durham
A letter to a Classics mailing list about the origin of and ease of calculation with Roman numerals.
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 Roman Numerals  Math Forum, Ask Dr. Math Common Question
A selection of answers to questions about Roman numerals, such as how they represented decimals and fractions; with memory aids for remembering what letter represents what value.
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 Roman Numerals  Math Forum, Ask Dr. Math FAQ
Basics: How do I read and write Roman numerals? What are the rules for subtracting letters? How do I write large numbers? Web resources: introductions, charts, calculators, and converters. Calculations: Did the Romans use fractions?
How can I use Roman
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