因为三角形ABC全等于三角形A1B1C1
AB=A1B1 AC=A1C1 BC=B1C1
又因为三角形A1B1C1全等于三角形A2B2C2
A1B1=A2B2 A1C1=A2C2 B1C1=B2C2
所以AB=A2B2 AC=A2C2 BC=B2C2
三边相等
所以三角形ABC全等于三角形A2B2C2