设AB中点F,FF'垂直蚂或B'C'。设AA'=a, BB'=b,CC'=c,GG'简塌=g,FF'=ff=(a+b)/2, 2f=a+bg=(2f+c)/3 证:CG:GF=2, 作CH//B'C', 交GG'于G'',交FF'于F'',GG''=2(f-c)/3,G''G'=c3g=2f+c3g=a+b+cAA'+BB'+CC'=3GG'闷咐伍