Editing Bisection (section)

===Quadrilateral===

The internal angle bisectors of a [[Convex polygon|convex]] [[quadrilateral]] either form a [[cyclic quadrilateral]] (that is, the four intersection points of adjacent angle bisectors are [[concyclic points|concyclic]]),<ref>

Weisstein, Eric W. "Quadrilateral." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/Quadrilateral.html</ref>  or they are [[Concurrent lines|concurrent]]. In the latter case the quadrilateral is a [[tangential quadrilateral]].

====Rhombus====

Each diagonal of a [[rhombus]] bisects opposite angles.

====Ex-tangential quadrilateral====

The excenter of an [[ex-tangential quadrilateral]] lies at the intersection of six angle bisectors. These are the internal angle bisectors at two opposite vertex angles, the external angle bisectors (supplementary angle bisectors) at the other two vertex angles, and the external angle bisectors at the angles formed where the [[Extended side|extensions of opposite sides]] intersect.