The first Fermat
point F1 of a triangle ABC is the perspective
center between ABC and the triangle having as vertices the vertices
added to the external Fermat triangles of
ABC.
The second
Fermat point F2 of a triangle ABC is the perspective
center between ABC and the triangle having as vertices the vertices
added to the internal Fermat triangles of
ABC.
They are also
called isogonic points. They are the points X(13) and X(14) in ETC.
