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.