Yff central triangle

1) Let X'Y'Z'  be the triangle bounded by the tangents to the incircle in their first intersections with the bisectors.
2) Let X"Y"Z" be the cevian triangle of the first mid-arc point M.
3) Let A' be the harmonic of X' with respect to A and X", and construct analogously B', C'. The Yff central triangle is A'B'C'.