The Longuet-Higgins circle is the radical circle of the circles centered at the vertices 
, 
, and 
of a reference triangle
with respective radii 
, 
, and 
. Its center is called the Longuet-Higgins
point and is Kimberling center 
. It has radius
 |
where 
is the circumradius of the reference
triangle, and circle function
 |
which corresponds to Kimberling center 
.
