X(3), X(4), X(23), X(32), X(67), X(76), X(98), X(511)
four foci of the MacBeath inconic : X(3), X(4) and two imaginary
K433 is an isogonal focal cubic with focus X(98), the Tarry point.
It is the locus of point P such that the segments X3-X32 and X4-X76 are seen from P under equal line angles.
It is also the locus of foci of inconics centered on the parallel at X(5) to the Brocard axis. This latter line is called the axis of the cubic.
See also CL051.
Compare K433 and K494 = nK(X3, X850, X6).