Question

如图,在三角形ABC中,角1=角2,角3=角4 ,角A=60,求证CD+BE=BC】

Answer 1

证明：在BC上取点F,使BE＝BF,连接IF∵∠A＝60∴∠ABC+∠ACB＝180-∠A＝120∵∠ABC＝∠1+∠2,∠1＝∠2∴∠ABC＝2∠2∵∠ACB＝∠3+∠4,∠3＝∠4∴∠ACB＝2∠4∴2∠2+2∠4＝∠ABC+∠ACB＝120∴∠2+∠4＝60∴∠BIE＝∠CI...