Definition:Excircle of Triangle/Exradius

Definition

 * Excircle-of-Triangle.png

A radius of an excircle of a triangle is called an exradius of the triangle.

In the above diagram, $r_a$ is the exradius of $\triangle ABC$ $a$.

Also known as
Some (usually older) sources hyphenate: ex-radius.

An exradius is also known as an eradius.