等式a2+b2+c2=ab+bc+ac等号两边均乘以2得:
2a2+2b2+2c2=2ab+2bc+2ac,
即a2-2ab+b2+a2-2ac+c2+b2-2bc+c2=0,
即(a-b)2+(a-c)2+(b-c)2=0,
解得:a=b=c,
所以,△ABC是等边三角形.
等式a2+b2+c2=ab+bc+ac等号两边均乘以2得:
2a2+2b2+2c2=2ab+2bc+2ac,
即a2-2ab+b2+a2-2ac+c2+b2-2bc+c2=0,
即(a-b)2+(a-c)2+(b-c)2=0,
解得:a=b=c,
所以,△ABC是等边三角形.