Isogonal Line

The line $L'$ through a Triangle Vertex obtained by reflecting an initial line $L$ (also through a Vertex) about the Angle Bisector. If three lines from the Vertices of a Triangle $\Delta ABC$ are Concurrent at $X=L_1L_2L_3$, then their isogonal lines are also Concurrent, and the point of concurrence $X'=L_1'L_2'L_3'$ is called the Isogonal Conjugate point.

See also Isogonal Conjugate

References

Johnson, R. A. Modern Geometry: An Elementary Treatise on the Geometry of the Triangle and the Circle. Boston, MA: Houghton Mifflin, pp. 153-157, 1929.