The Compendium Geometry is an eBook providing facts, formulas and explanations about geometry.

Home Analytic Geometry Quadrilateral Tangential Quadrilateral
See also: Quadrilateral - General Definitions, Parallelogram and Rhombus, Cyclic Quadrilateral 
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Tangential Quadrilateral

A tangential quadrilateral is one for which an incircle can be constructed. This means that all four sides of the quadrilateral are tangent to the incircle.

The opposite sides of a tangential quadrilateral satisfy the following equation:

a + c = b + d = s,

with s being half of the perimeter (semiperimeter). The area of the tangential quadrilateral can be calculated by

A = sr,

with r being the radius of the incircle.

Please note that a rhombus is a special case of a tangential quadrilateral.

Home Analytic Geometry Quadrilateral Tangential Quadrilateral

Last Update: 2010-12-06