设 DE = x ,则 DF = DE = x ,
已知,DF∥BC,则GH正三角形△DEF的高,
可得:GH = (√3/2)x ,AG/AH = AF/AC = DF/BC ,
其中,AG = AH-GH = 6-(√3/2)x ,AH = 6 ,DF = x ,BC = 4 ,
可得:[6-(√3/2)x]/6 = x/4 ,
解得:x = 6-2√3 ;
所以,DE = 6-2√3 .
设 DE = x ,则 DF = DE = x ,
已知,DF∥BC,则GH正三角形△DEF的高,
可得:GH = (√3/2)x ,AG/AH = AF/AC = DF/BC ,
其中,AG = AH-GH = 6-(√3/2)x ,AH = 6 ,DF = x ,BC = 4 ,
可得:[6-(√3/2)x]/6 = x/4 ,
解得:x = 6-2√3 ;
所以,DE = 6-2√3 .