Consider three lines concurring at G and three circles c1, c2, c3 tangent at these three lines. Then the other inner common tangents of the circles are also concurrent at a point H. H is isogonal conjugate of G w.r. to the triangle formed by the intersection points of the inner tangents of the three circles. The definition of Isogonal-Conjugation can be found in the file: Isogonal_Conjugation.html .