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Home  Analytic Geometry Triangle Excircle of a Triangle |
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| See also: Altitudes of a Triangle, Incircle and Angle Bisectors of a Triangle, Circumcircle of a Triangle | ||||
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Excircle of a Triangle
 The excircle is the circle whose center is defined by the intersection of the external angle bisectors of two vertices A and B (angles α' and β'), and which is tangent to the side c between the two vertices. The excircle is also tangent to the extension of the sides a and b.
Each triangle has three excircles, whose radii are determined by the following equations:
Note that the excircles are not necessarily tangent to the incircle.
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Last Update: 2011-01-11