Exterior Angle Bisector Theorem
- Author:
- Brian Sterr
- Topic:
- Geometry
Theorem
An angle bisector of an exterior angle of a triangle divides the opposite side externally into segments proportional to the adjacent sides.
Setup for Proof
Given: bisects the exterior angle of at .
Prove:
Construction:
Construct parallel to through , intersecting at
Explore
Move to change the type of triangle for .
Will the angle bisector always intersect ?