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 TOPICS This page:   Euclidean/plane   geometry    Search   Dr. Math See also the Dr. Math FAQ:   geometric formulas Internet Library:   Euclidean/plane   geometry 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 Euclidean/Plane Geometry Stars indicate particularly interesting answers or good places to begin browsing. Selected answers to common questions:     Classifying quadrilaterals.     Pythagorean theorem proofs. Building a Geometric Proof [06/03/1999] Can you explain how to do a two-column proof? Explementary Angles [05/29/2003] What do we call two angles that add up to 360 degrees? Geometry Proofs [11/07/2001] General and specific advice for a student having trouble writing proofs on her own. Is a Sphere 2-D or 3-D? [8/8/1996] Is a sphere a two- or a three-dimensional object? Measuring Angles with a Protractor [02/28/2002] I want to know how to measure acute, reflex and obtuse angles with a protractor. Painting Cubes [01/06/2003] How many unit cubes would be needed to create a cube with a side length of 3 units? If you painted the larger cube and broke it up into unit cubes, how many faces of each unit cube would be painted? Remembering Area Formulas [12/23/2001] Is there was a good way to help me memorize the formulas for areas of different shapes? About Basic Geometry [10/14/1998] Who developed basic geometry? What is it used for? Who uses it? Abraham Kaestner and Euclid's Fifth (Parallel) Postulate [12/02/1996] Where can I find information on Abraham Kaestner? A-frame for Swing [07/26/1997] I am trying to build a stand for a swing. The ends are A-frames out of 4 by 4's... what is the angle of the miter cut? The Algebra of Complements and Supplements [01/25/1999] What are complements and supplements? How do you translate these concepts into algebra? Alternate and Corresponding Angles [10/21/1996] Please explain corresponding and alternate angles. Alternate Exterior Angles [06/03/2002] What is an 'alternate exterior angle'? Analytical Geometry [04/11/2002] When two straight lines meet each other perpendicularly, the product of their slopes is -1. However, x and y axes meet at 90 degrees, but the product of their slopes is not -1. Why? Angle Inscribed in a Semicircle [11/07/2001] Prove that any angle inscribed in a semicircle is a right angle. Angles as Turns [05/29/2003] How can angles be negative? Angles Greater than 360 Degrees [01/01/1999] We know the definitions of acute, obtuse, and reflex angles, but we were debating what kind of angle a 425 degree angle is. Angle, Side Length of a Triangle [9/4/1996] What is the relation between the angles and side lengths of a triangle? The Angles of a Roof [11/20/1995] I am trying to build a model house but am having trouble with laying out the roof. The main part of the house has a peaked roof (an "A" frame house); the angle formed when the roof meets the ground is 60 degrees. There is an addition onto the A-frame with a 30 degree angle formed to the walls. What angle should the addition's roof be cut at so it meets the A-frame roof? Angles of Stars [08/18/1997] What are the interior and external angles of stars built on regular pentagons and octagons. Angle Trisection: Construction vs. Drawing [10/17/2001] Has anyone ever divided an angle into three equal parts by construction? I have been told it has not been accomplished. Another Grazing Cow [6/7/1995] A man has a barn that is 20 ft by 10 ft. He tethers a cow to one corner of the outside of the barn using a 50-ft rope. What is the total area that the cow is capable of grazing? Ant and Rectangle [01/22/2001] Does the ant walk along the diagonals of the rectangle? Area and Perimeter: Isoperimetric Quotient [12/05/2001] What is the isoperimetric quotient of a two-dimensional shape? Is it a measure of compression? Area and Perimeter: Mowing the Lawn [6/1/1996] How many circuits are necessary to cut half the lawn? Area, Circumference of an Ellipse [7/29/1996] How do I calculate the area and circumference of a given ellipse? Are All Triangles Isosceles? [09/15/1999] Can you help me find the flaw in this 'proof' claiming that all triangles are isosceles? Are Angles Dimensionless? [08/31/2003] If you look at the dimensions in the equation arc length = r*theta, it appears that angles must be dimensionless. But this can't be right. Or can it? Area of a Circle with Radius less than 1 [02/18/2002] If the radius is less than 1 it just gets smaller and you get a smaller area... Area of an Ellipse Cut by a Chord [05/26/2000] How can you calculate area of the part of an ellipse cut off by a chord, if you know the major and minor axes, and the chord? 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 a Rectangle Outside a Rectangle [6/11/1996] Find the area of the concrete border of a rectangular swimming pool. Area of a Reuleaux Triangle [06/13/2002] Could you please help me find a formula to find the area of a Reuleaux triangle? Area of Intersection of Two Circular Segments [04/20/2007] Given a circle of radius r and center c, suppose two intersecting chords AB and CD (intersecting in P) form two circular segments. How do I compute the area of the intersection of the two circular segments? Areas of House Lots [02/18/1998] We have to determine sanitary sewer assessments of properties based on the square feet of their lots. Many lots are 4-sided but do not have any parallel lines... Arrange 7 Points in a Plane... [10/05/1998] Arrange 7 points in a plane so that if any three are chosen, at least 2 of them will be a unit distance apart. Azimuth Angle [09/08/1998] Can you give me the formula for the azimuth angle and explain some of the terminology? Ball Bouncing off a Line Segment [05/04/2001] If you take an arbitrary line on a 2D plane, e.g. x1y1 - x2y2, then take a point that moves about the plane, say pxpy, can you tell if this point has crossed the line at any time? Barycentric Calculus [01/06/1999] How does barycentric calculus compare with trilinear or cartesian calculus? Betweenness of Points on a Line Idea and Proof [06/26/2008] Could someone explain betweenness of points on a line and why it's important? I also don't understand the way my book proves it. Page:  1  2  3  4  5  6  7  8  9 [next>]

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