The Compendium Geometry is an eBook providing facts, formulas and explanations about geometry. 
Home Analytic Geometry Triangle Incircle and Angle Bisectors  
See also: Circumcircle of a Triangle, Excircle of a Triangle, Properties of a Right Triangle  
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Incircle and Angle Bisectors of a TriangleThe angle bisectors of a triangle are the lines which cut the inner angles of a triangle into equal halves. The angle bisectors are concurrent and intersect at the center of the incircle (incenter S). Each side of a triangle is cut by the corresponding angle bisector into two segments whose lengths are related to the lengths of the adjacent sides: The lengths of the angle bisectors are given by
The radius r of the incircle can be calculated from the area A of the triangle:


Home Analytic Geometry Triangle Incircle and Angle Bisectors 