1. (2021七下·沧县期中) 如图，AB和CD相交于点O，E为线段AC上一点，过点E作EFAB交DB延长线于F，∠C＝∠COA，∠D＝∠BOD．

求证：∠A＝∠F，下面是小明同学进行的说理，请你将小明同学的说理过程或说理根据补充完整．

证明：∵∠C＝∠COA，∠D＝∠BOD（已知），

且∠COA＝∠BOD（                  ▲                  ）．

∴∠C＝                  ▲                  （                  ▲                  ）．

∴ACDF（                  ▲                  ）．

∴∠A＝                  ▲                  （                  ▲                  ）．

∵EFAB（已知），

∴∠F＝                  ▲                  （                  ▲                  ）．

∴∠A＝∠F（                  ▲                  ）．