已知△ABC和△A'B'C',D为AC中点,D'为A'C'中点,且AB/A'B'=AC/A'C'=DB/D'B'
求证△ABC∽△A'B'C'
证明D,D'为中点,则AD/AC=A'D'/A'C'
则AD/A'D'=AB/A'B'=DB/D'B'
可证△ABD∽△A'B'D'
则∠A=∠A'
∵AB/A'B'=AC/A'C'
∴△ABC∽△A'B'C'