Difference between revisions of "Quadrilateral"
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A quadrilateral is a [[polygon]] with four sides. | A quadrilateral is a [[polygon]] with four sides. | ||
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| + | As a consequence of the definition, the sum of the angles in a quadrilateral equal 360<sup>0</sup>, and all quadrilaterals are capable of [[tessellation|tessellating]] an [[infinite]] plane. | ||
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| + | ===Classification of Quadrilaterals=== | ||
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| + | The [[classification]] of quadrilaterals is complex, as there are several intersecting sub-categories: | ||
| + | * A (British) [[trapezium]] or (American) [[trapezoid]] has one pair of opposite sides parallel. A version of this called the [[isoceles trapezium]] also has one pair of opposite sides equal | ||
| + | * A [[parallelogram]] has two pairs of opposite sides parallel (and equal) | ||
| + | * A [[rectangle]] has four right angles | ||
| + | * A [[rhombus]] has four equal sides | ||
| + | * A [[kite]] has two pairs of adjacent equal sides | ||
| + | * A [[re-entrant quadrilateral]] has one internal angle greater than 180<sup>0</sup> | ||
| + | * An [[arrowhead]] is a re-entrant [[kite]] | ||
| + | * A [[square]] is both a [[rectangle]] and a [[rhombus]] | ||
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[[Category:Geometry]] | [[Category:Geometry]] | ||
Revision as of 11:06, May 14, 2007
A quadrilateral is a polygon with four sides.
As a consequence of the definition, the sum of the angles in a quadrilateral equal 3600, and all quadrilaterals are capable of tessellating an infinite plane.
Classification of Quadrilaterals
The classification of quadrilaterals is complex, as there are several intersecting sub-categories:
- A (British) trapezium or (American) trapezoid has one pair of opposite sides parallel. A version of this called the isoceles trapezium also has one pair of opposite sides equal
- A parallelogram has two pairs of opposite sides parallel (and equal)
- A rectangle has four right angles
- A rhombus has four equal sides
- A kite has two pairs of adjacent equal sides
- A re-entrant quadrilateral has one internal angle greater than 1800
- An arrowhead is a re-entrant kite
- A square is both a rectangle and a rhombus
