The de Longchamps circle is defined as the radical circle of the power circles of a given reference triangle. It is defined only for obtuse triangles.
It is the complement of the polar circle.
It has circle function
 |
corresponding to Kimberling center 
. Its center is the de
Longchamps point 
(
), and its radius is
 |
where 
is the circumradius of the reference triangle.
No Kimberling centers lie on the de Longchamps circle.
