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Home  Analytic Geometry Quadrilateral Quadrilateral - General Definitions |
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| See also: Triangle - General Definitions, Cyclic Quadrilateral, Kite, Parallelogram and Rhombus, Rectangle and Square, Tangential Quadrilateral, Trapezoid, Varignon Parallelogram, Regular Polygon | |
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Quadrilateral - General Definitions
A quadrilateral is a four-sided polygon, which is sometimes also called "quadrangle" or "tetragon". All four vertices of the quadrilateral have to lie on a plane, otherwise it is called a "skew quadrilateral".
One can differentiate between three topologies: convex quadrilaterals (left figure), concave quadrilaterals, and crossed quadrilaterals. The sum of the angles in a (non-crossed) quadrilateral is 360°: α + β + γ + δ = 360. The area A of a convex planar quadrilateral is given by
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Last Update: 2011-01-11