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Home Mathematics Analytic Geometry Quadrilateral Quadrilateral - General Definitions |
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| See also: Triangle - General Definitions, Trapezoid, Rectangle and Square, Parallelogram and Rhombus, Varignon Parallelogram, Tangential Quadrilateral, Cyclic Quadrilateral, Kite | |
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°: a + b + g + d = 360. The area A of a quadrilateral is given by
A = 0.5 j = (a + g)/2 = (b + d)/2
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