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 TOPICS This page:   triangles/polygons    Search   Dr. Math See also the Dr. Math FAQ:   geometric formulas and   naming polygons   and polyhedra and   Pythagorean theorem Internet Library:   triangles/polygons MIDDLE SCHOOL About Math Algebra    equations    factoring expressions    graphing equations Arithmetic    division    exponents    factorials    factoring numbers    fractions/percents    logarithms Definitions Geometry    2-dimensional      conic sections/        circles      triangles/polygons    3D and higher      polyhedra History/Biography Logic Measurement    calendars/      dates/time    temperature    terms/units Number Sense    factoring numbers    negative numbers    pi    prime numbers    square roots Probability Puzzles Ratio/Proportion Statistics Word Problems Browse Middle School Triangles and Other Polygons Stars indicate particularly interesting answers or good places to begin browsing. Selected answers to common questions:     Classifying quadrilaterals.     Polygon diagonals.     Pythagorean theorem proofs. Naming Corresponding Parts of Congruent Figures [04/23/2003] Given triangle OPS congruent to triangle TQR, name the corresponding sides and angles of the two triangles. Naming Polygons [5/30/1995] Could you please give me a complete list of polygon names from 3 - 100? Naming the Isosceles Triangle [09/23/1998] How did the isosceles triangle receive its name? Nonagon or Enneagon? [02/06/2003] Is 'enneagon' really the correct name for a 9-sided polygon? Number of Points in a Star [7/16/1996] Is there a way to predict the number of points in a star given only the internal angle of the corners? One- and Two-sided Polygons [12/07/1999] Can you explain what a monogon and a digon are? On Polygons, Polygons within Polygons, and Definitions [07/22/2010] If we cut one polygon out of the interior of another, is the resulting shape a polygon? Doctor Peterson gives a curious student a better definition than he found in his book, pointing out the importance of separating polygons from their interiors -- and of experimenting with definitions. Origami Equilateral Triangle [04/26/2001] How can I create an equilateral triangle from a piece of paper using only origami-like folds? Origin, Meaning of 'Hypotenuse' [9/13/1996] What is the origin and meaning of the term "hypotenuse"? Parallelogram Perimeter [10/01/1997] The diagonals of a parallelogram are 10 and 24 in length. If one side of the paralellogram is 13, what is the perimeter? Pentagram [12/08/2001] Is a five-pointed star on a flag a decagon? Or just five triangles? Perimeter of Two Similar Objects [2/16/1996] Why do you lose area in a 4 x 12 rectangle as compared to an 8 x 8 square? Each has the same perimeter. Picture of Icosahedron [7/31/1996] Do you have a picture of an icosahedron? Pipe Needed for Natural Gas Line [09/03/1997] Two houses are 130 metres apart at distances of 55 and 105 metres... Placing Coins That Touch [8/7/1996] How many 20-cent coins can you put around a 20-cent coin so that all of them touch? Pole in a Box [02/09/1999] Can a pole 6.5m long fit into a truck with dimensions of 3m, 3.5m, and 4m? Polygon Diagrams [05/11/2003] I would like to see pictures of polygons with 11, 12, 13, 14, and 15 sides. Polygon Names [09/18/2001] Why is a 3-sided polygon called a triangle instead of a tri-gon? Why is a 4-sided polygon called a quadrilateral instead of a tetragon, when all the others are ___-gons? Why is there not a single consistent term? Polygon Names II [12/11/2003] Why is the triangle named "triANGL"', unlike all the other polygons, which have names like "quadriLATERAL" or "pentaGON"? Polygons and Circles [4/3/1996] Is a circle a polygon? Why or why not? Polygons, Infinite Sides, and Circles [04/03/1997] Can a regular polygon with an infinite number of sides be a circle? Polyominoes [09/08/1997] I am using polyominos, but I do not know how to tell my dad what they are. How can I tell him so he will know? Proof of Pythagorean Theorem: Pythagoras' Reasoning [02/23/1998] I would like to know how Pythagoras reasoned his theorem. Proofs with Isosceles Triangles [10/28/1998] What are altitudes, angle bisectors, and medians? How do you prove that in an isoseles triangle, the altitude is a median and an angle bisector? Properties of Equilateral Triangles [07/20/1998] If ABC is equilateral and AD is one of its heights, what are the measures of the angles? Is ADB equal to ADC? If AB = 2 find BD and AD. Prove Triangles are Similar [12/16/1995] How do you prove two triangles are similar? Pythagorean Theorem [1/19/1995] What is the Pythagorean Theorem? Pythagorean Theorem [7/19/1995] How come a^2 + b^2 = c^2? Pythagorean Theorem [5/14/1996] What is the Pythagorean theorem? The Pythagorean Theorem: A Modern Proof [04/14/1997] I know that the Pythagorean Theorem works and I can show how it works, but why does it work? Pythagorean Theorem Legend [01/31/2009] Is there a Sioux Indian legend that refers to the Pythagorean Theorem? Pythagorean Theorem Proof by Brodie Explained [03/15/2000] Could you give me a step-by-step explanation of Dr. Scott Brodie's proof of the Pythagorean theorem given at the cut-the-knot website? Pythagorean Theorem Proof: Four Right Triangles [10/7/1996] I don't understand the Pythagorean Theorem. Pythagorean Triples [04/14/1997] Why can't all the numbers in a Pythagorean triple be prime? Quadrilateral Classification: Definition of a Trapezoid [01/15/1997] What is the correct definition of a trapezoid, and why? Quadrilateral Patterns [03/06/1997] What is the formula that gives the number of quadrilaterals within a square grid when you increase the square grid by one unit on each side? Quadrilaterals [8/31/1995] What is 4-sided and has no equal angles? Ratio and proportion [12/5/1994] I need extra help in ratio and proportion. Ratio of Sides and Ratio of Areas [02/11/1999] If the sides of a triangle are in the ratio of 1:7, what is the ratio of their areas? What about for other shapes? Ratios and Geometry [10/29/1998] An airplane flying at 33,000 feet has a visibility of 100 miles. What percent of the total land area to the horizon is visible? Page: []

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