证明：在AB的延长线上取点E,使BE＝BC＝2,连接CE,取AB的中点D,连接CD∵BE＝BC＝2∴∠E＝∠ECB∴∠ABC＝∠E+∠ECB＝2∠E∵D为AB的中点,AB＝4∴BD＝AD＝AB/2＝2∴∠BCD＝∠BDC,AD＝BE∴∠ECD＝∠ECB+∠BCD＝∠E+∠BDC∵...