The (interior) bisector of an angle , also called the internal angle bisector (Kimberling 1998, pp. 11-12), is the line
or line segment that divides the angle into two equal
parts.
The angle bisectors meet at the incenter trilinear
coordinates 1:1:1.
The length angle triangle
where
The points trilinear coordinates incentral
triangle .
See also Angle ,
Angle Bisector Theorem ,
Angle Trisection ,
Cyclic
Quadrangle ,
Exterior Angle Bisector ,
Incenter ,
Incentral
Triangle ,
Incircle ,
Isodynamic
Points ,
Orthocentric System ,
Steiner-Lehmus
Theorem
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References Altshiller-Court, N. College Geometry: A Second Course in Plane Geometry for Colleges and Normal Schools, 2nd
ed., rev. enl. Coxeter,
H. S. M. and Greitzer, S. L. Geometry
Revisited. Dixon,
R. Mathographics. Kimberling, C. "Triangle Centers
and Central Triangles." Congr. Numer. 129 , 1-295, 1998. Mackay,
J. S. "Properties Concerned with the Angular Bisectors of a Triangle."
Proc. Edinburgh Math. Soc. 13 , 37-102, 1895. Pedoe, D.
Circles:
A Mathematical View, rev. ed. Referenced on Wolfram|Alpha Angle Bisector
Cite this as:
Weisstein, Eric W. "Angle Bisector." From
MathWorld https://mathworld.wolfram.com/AngleBisector.html
Subject classifications
, which has trilinear
coordinates 1:1:1.
of the bisector 
of angle 
in the above triangle 
is given by
![t_1^2=a_2a_3[1-(a_1^2)/((a_2+a_3)^2)],](/images/equations/AngleBisector/NumberedEquation1.svg)
and 
.
,
, and 
have trilinear coordinates 
, 
, and 
, respectively, and form the vertices of the incentral
triangle.
