Angle bisector

Important

Given an angle $ABC$ , the angle bisector is a ray $BD$ that starts at the vertex $B$ and divides the angle $ABC$ into two angles, $ABD$ and $DBC$ , such that $\angle ABD = \angle DBC = \frac{1}{2}\angle ABC$ .

Important properties

Every angle has exactly one unique angle bisector.
The angle bisector always passes through the vertex of the angle.
In a triangle, the three angle bisectors meet at a single point called the incenter, which is the center of the circle inscribed in the triangle.