题目

如图，AD是△ABC的角平分线，DE∥AB，DF∥AC，EF交AD于点O．请问：DO是△DEF的角平分线吗?请说明理由． 答案：【答案】DO是△DEF的角平分线．证明：∵AD是△ABC的角平分线，∴∠EAD=∠FAD．∵DE∥AB，DF∥AC，∴∠EDA=∠FAD，∠FDA=∠EAD （2分）∴∠EDA=∠FDA．∴DO是△DEF的角平分线． （4分）【解析】利用平行线的性质以及角平分线的性质求出∠EDO=∠FDO即可.DO是△DEF的角平分线，理由是：∵AD是△ABC的角平分线．∴∠EAD_______ with her sister, Mary is even more hardworking and better at her lessons. A. Compare     B. To compare    C. Comparing     D. Compared