解：①在?$BC$?上取?$D、$??$E、$??$F，$?使?$BE=ED=DF=FC，$?連接?$AE、$??$AD、$??$AF$?
②分別取?$BC、$??$CA$?的中點(diǎn)?$D、$??$F，$?再取?$BD$?的中點(diǎn)?$E，$?連接?$AE、$??$AD、$??$DF$?
③分別取?$AB、$??$BC、$??$CA$?的中點(diǎn)?$E、$??$D、$??$F，$?連接?$DE、$??$AD、$??$DF$?
④分別取?$BC、$??$CA$?的中點(diǎn)?$D、$??$F，$?連接?$AD、$??$DF，$?再取?$AD$?的中點(diǎn)?$E，$?連接?$BE.$?
