令BD与CE相交于O.∵AB＞AC,∴∠ACB＞∠ABC,又∠ABD＝∠CBD＝∠ABC/2、∠ACE＝∠BCE＝∠ACB/2,∴∠DCO＞∠OBE,∴一定能在线段OD上取一点F,使∠OCF＝∠OBE,∴B、C、F、E共圆.由三角形内角和定理,有：∠A＋∠ABC＋∠ACB...
