Let Ha, Hb, Hc be the altitude feet; Ma, Mb, Mc the midpoints of the sides; Ga, Gb, Gc the centroids of HaMbMc, HbMcMa, HcMaMb (altimedial triangles) and ga, gb, gc the centroids of MaHbHc, MbHcHa, McHaHb. The lines Gaga, Gbgb, Gcgc concur.