 PUERTRA  Javier Sánchez González
The software package PUERTRA implemented a theoretical study of formal properties of Islamic geometrical art. PUERTRA modeled the Islamic rectilinear interlaced lattices found extensively in wood work (artesonado ceilings, mosque minbars, doors and windows,
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 Regular Polygon Formulas (Ask Dr. Math FAQ)  Math Forum
Formulas for finding the area, perimeter, etc. of a regular polygon, and constructing regular polygons with compass and straightedge, in particular the pentagon.
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 Religious Beliefs Made Visual: Geometry and Islam  Jane Norman, Consultant, Metropolitan Museum of Art
Although the shapes and structures are based on the geometry of Euclid and other Greek mathematicians, Islamic artists used them to create visual statements about religious ideas. A discussion of the use of geometric motifs in Islamic art, with instructions
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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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 SafeT Compass  Maddy, Maverick; James Garner
A compass with no sharp points, flat enough to use as a bookmark in a high school geometry or algebra text and safe enough for a child. Draw circles from 1/4 in. to 10 in. in diameter with this new flat compass. $2 each, 2 for $3 postpaid. See also their
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 The Siluroid Curve  Dario de Judicibus
Formulas, graphs, compassandstraightedge constructions, derivatives, and more about this biquadratic, trilobate curve. Among the torpedo or fishshaped curve's curious properties: connecting its intersection with the generatrix or goniometric circle
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 Sketches for Cabri Geomètre (v. 1)  L. J. Dickey, University of Waterloo
Cabri Geomètre (the original version of of the program) figures to download (binhexed): Conic Given by Five Points; Ten Sketches of Desargues Theorem; Harmonic Conjugates; The Inverse of a Circle; The Inverse of a Line; The Inverse of a Point;
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 Some Golden Geometry  Rashomon (K. Wiedman)
The Golden Mean is a ratio that is present in the growth patterns of many things  the spiral formed by a shell or the curve of a fern, for example. This page (also found at http://tony.ai/KW/goldengeom.html) gives instructions for constructing the Golden
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 Squaring the Circle  MacTutor Math History Archives
Linked essay covering the problem of squaring the circle in the form which we think of it today, which originated in Greek mathematics: given a circle, construct geometrically a square equal in area to the given circle. This article discusses the history
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 Tangent Circles  Paul Kunkel
Three circles are given. How many circles can be constructed tangent to all three? How are they constructed? This lesson includes ten applets, to cover all of the special cases. Some of them are very complex.
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 Teen Math Whizzes Go Euclid One Better  Gautam Nair, The Wall Street Journal
The scholarly journal Mathematics Teacher has churned out some 7,500 articles published over the past nine decades. This month, Volume 90, issue No. 1 will feature a first: a formal math treatise by two high school students. A reproduction of an article
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 There are trisectable angles that are not constructible  Interactive Mathematics Miscellany and Puzzles, Alexander Bogomolny
Why certain angles that are trisectable cannot be constructed by traditional methods.
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 Things Impossible  Interactive Mathematics Miscellany and Puzzles, Alexander Bogomolny
Essays on impossible things, including trisecting an angle, doubling a cube, squaring a circle, moving pegs five places in one direction (via checkerjumps), finding the center of a given circle with the straightedge alone, representing the square root
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 Tips & Tricks to Gothic Geometry  Joe Chiffriller; NewYorkCarver.com
The geometry of gothic cathedrals: how to construct a trifoil design, an ogee arch, and a rose window. With links to cathedral and castle tours.
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 Toys from Trash  Arvind Gupta
Stepbystep photographic instructions for building elegantly simple, colorful "Math Magic" doityourself manipulatives: Abacus, Flexagon, Triangle Grid, Flat Flexagon, Slipper Insets, Folding Pentagon, Tangram, Paper Octagon, Cylinder and Cone, Area
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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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 Wonders of Ancient Greek Mathematics  Timothy Reluga; Tufts University
An arbitrary collection of interesting solutions to geometric problems discovered and solved by the Greeks, limited to intuitive, elegant, or beautiful solutions and some that do not meet these requirements, serving as reminders of the level to which
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