a²+b²+c²=ab+bc+ca2(a²+b²+c²)=2(ab+bc+ca)(a²-2ab+b²)+(b²-2bc+c²)+(a²-2ac+c²)=0(a-b)²+(b-c)²+(a-c)²=0a-b=0,b-c=0,a-c=0a=b=c等边...