过c点做CM⊥AB,交AB于MCM=BC/2=5AB=5√3=5BD, BD=√3, BM=AB/2=2.5√3当△FDE是等边三角形乱行时,EF值最小,即:DF=DE=EF此时消陪祥∠BDE=90°,拿搏即:△BDE∽△BMCBM/BD=CM/DE, DE=5√3/2.5√3=2即:EF=DE=2