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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 HIGH SCHOOL About Math Analysis Algebra    basic algebra    equations/graphs/      translations    linear algebra    linear equations    polynomials Calculus Complex Numbers Calculators/    Computers Definitions Discrete Math    permutations/    combinations Exponents    Logarithms Fibonacci Sequence/   Golden Ratio Fractals Functions Geometry    Euclidean/plane      conic sections/        circles      constructions      coordinate plane      triangles/polygons    higher-dimensional      polyhedra    non-Euclidean    practical geometry    symmetry/tessellations History/Biography Interest Logic Negative Numbers Number Theory Physics/Chemistry Probability Projects Puzzles Sequences/Series Sets Square/Cube Roots Statistics Transcendental   Numbers Trigonometry Browse High School Triangles and Other Polygons Stars indicate particularly interesting answers or good places to begin browsing. Selected answers to common questions:     Area of an irregular shape.     Classifying quadrilaterals.     Heron's formula.     Polygon diagonals.     Pythagorean theorem proofs.     Triangle congruence. Area and Perimeter: Mowing the Lawn [6/1/1996] How many circuits are necessary to cut half the lawn? Are All Triangles Isosceles? [09/15/1999] Can you help me find the flaw in this 'proof' claiming that all triangles are isosceles? Area of a Half-Mowed Yard [08/21/2003] There is a square/rectangular yard, size unknown. You have mowed a 10 foot swath around the perimeter. You are now half done. How big is the yard? Area of a Hexagon [7/9/1996] How do you calculate the area of a hexagon? Area of a Lawn [09/04/2002] I have two areas of lawn that I want to sod with new grass and don't know how much sod to buy. Area of an Inscribed Quadrilateral [05/11/2000] Given a quadrilateral where the midpoints of each side are connected to form a new quadrilaterals inside the first, what is the ratio of the area of the larger quadrilateral to the smaller one? Area of an Irregular Polygon Given Side Length [8/2/1996] What is the area of an irregular quadrilateral with side lengths in a clockwise order of 43.61, 133.64, 146.96, and 110.85? Area of an Octagonal House [08/24/2003] I plan to build an octagonal home, and would like to know the area of the completed home if each wall span is 14 feet in length. Area of an Unspecified Triangle [6/1/1996] A square ABCD, with side "y", and an equilateral triangle DEF, with the same side "y", are in contact at point "d"... Area of an Unusual Hexagon [12/05/1996] Find the area of a hexagon made from a triangle with squares appended to each of its sides and three more triangles each consisting of one unknown side and two sides which are shared with two of the squares. Area of a Polygon [06/27/1997] If you know the coordinates of the vertices, how do you calculate the area of a polygon? Area of a Rectangle Outside a Rectangle [6/11/1996] Find the area of the concrete border of a rectangular swimming pool. Area of a Regular Octagon [10/27/1999] How do you find the area of a regular octagon? Area of a Regular Octagon: Proof of a Formula [08/31/1998] A proof of the formula. Area of a Rhombus and Area of a Square [11/16/2007] A rhombus has four equal sides, so it's a 'pushed over' square. Why is the area formula not side times side like in a square? Area of a Right Triangle [02/09/2002] Find the area of a right triangle that has a perimeter of length 16 meters and a hypotenuse with length 7 meters. The Area of a Roof [05/18/2002] How can I determine the area of a hipped roof for a building 100 feet long and 80 feet wide, with a pitch of 6/12, and 3 feet of overhang for the eaves? The Area of a Square Inscribed in a Circle [12/23/1995] What is the area of a square inscribed in a circle whose circumference is 16 (pi). Area of a Trapezoid [04/27/1997] Find the area of a trapezoid with three sides of length 80 and one of length 120. Area of a Triangle [6/2/1996] Knowing one side measures 1 and two adjacent angles measure a and b... Area of Bermuda Triangle [06/10/2001] The Bermuda triangle is shown on a graph with the points A(1,2) B(4,8) and C(8,1). Determine the area of the triangle two different ways. Area of Equilateral Triangle [12/06/2002] Equilateral triangle ABC has, near its center, point P, which is 3, 4, and 5 units from the three vertices. What is the area of triangle ABC? Area of Inscribed Circle [12/01/1998] Find the area of the circle inscribed in a triangle ABC using Heron's Law. Area of Polygon [08/20/1999] Using coordinate system to find the areas of polygons. Area of Quadrilateral, Given Angles and Two Opposite Sides [05/13/2002] If I have a quadrilateral with all the angles known and two opposite sides known, can I find the area? Area of Trapezoid Given Only the Side Lengths [12/15/2008] How do you find the area of a trapezoid if all you are given is the four side lengths and you don't know which pair of sides is parallel? The Area of Triangles using Hero's Formula [12/13/1995] If a person gave three dimensions of a triangle (in feet) and noted the base dimension, without knowing the angles because the other two lines would have to intersect someplace, is there a formula that could calculate the area? Area of Triangles When Altitudes Are Given [12/16/2002] Find the area of a triangle when the lengths of the three altitudes are given. Area, Perimeter, and Congruency of Quadrilaterals [06/23/2003] I'm trying to find out how to prove or disprove if it is always true that if two quadrilaterals have the same area and the same perimeter, they will always be congruent. Areas of N-Sided Regular Polygon and Circle [02/24/2005] The area of an n-sided regular polygon approaches the area of a circle as n gets very large. Attempt at Trisecting an Angle [11/08/1999] Can the arcs of the two circles formed by the construction described be the same length? Would this construction trisect the angle? Axes of Symmetry [2/3/1996] Can you help a year 5 student understand axes of symmetry of a triangle? Base or Width? [06/11/2002] When computing area, is there a difference between 'width' and 'base'? Bounding Rectangle for an Ellipse [6/28/1996] I would like to know if there is a general equation for a bounding rectangle of an ellipse. Break a dowel to form a triangle [3/8/1995] A wooden dowel is randomly broken in 2 places. What is the probability that the 3 resulting fragments can be used to form the sides of a triangle? Broken Flag Pole [9/11/1996] A 90 ft high flag pole sits atop and in the corner of a 10 ft high, 10 ft wide building. The pole breaks... Building a Cone [10/28/2001] I am trying to find a formula for building a cone for a chimney flashing. It should be 21" tall with a top opening of 8", a bottom opening of 20", and a vertical seam overlap of 2". Building a Skateboard Ramp [9/19/1995] I'm trying to build a skateboard ramp, pyramid with flat top, height one foot, angle of ascent thirty degrees, other angles ninety degrees and sixty degrees. Building Squares with Tangram Puzzle Pieces [03/21/2006] Is it possible to build a square using only 6 of the 7 pieces of the well-known Tangram puzzle? Calculating Areas of Quadrilaterals and Triangles [08/30/2005] What portion of an acre is a plot of land that is 85 x 174 x 73 x 118? How about a plot of land that is 150 x 118 x 150? Page: []

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