Let Ab be the intersection between
AC and the perpendicular to BC from B. Let Ac the intersection between
AB and the perpendicular to BC from C. Define cyclically Bc, Ba, Ca, Cb.
Then:
1) The six points Ab, Ac, Bc, Ba,
Ca, Cb lie in a conic.
2) A', B', C' being the midpoints
of AbAc, BaBc, CaCb, the lines AA', BB', CC' concur.
3) A”, B”, C” being the midpoints
of BaCa, CbAb, AcBc, the lines AA”, BB”, CC” concur at the De Longchamps
point L.
4) A*, B*, C* being the midpoints
of BcCb, CaAc, AbBa, the lines AA*, BB*, CC* concur at the symmedian K.