ab = ac，AE⊥BC

∴BE=CE

Similarly, AD=BD AF=CF

∴DF=﹙ 1/2﹚BC、DE=﹙ 1/2﹚AC、EF=﹙ 1/2﹚AB

∵ Triangle ABC is an equilateral triangle, and AB=AC=BC.

∴DF=DE=EF

△ def is an equilateral triangle.