Bisectors in a Triangle

Perpendicular bisector

The perpendicular bisector of a side of a triangle a line perpendicular to the side and passing through its midpoint.

The three perpendicular bisectors of the sides of a triangle meet in a single point, called the circumcenter.

The circumcenter is equidistant from the vertices of the triangle.  (See circumcenter theorem.)

Angle bisector

The angle bisector of an angle of a triangle is a straight line that divides the angle into two congruent angles.

The three angle bisectors of the angles of a triangle meet in a single point, called the incenter.