已知,EB = EC ,可得：∠C = ∠EBC = (1/2)∠B .在DC上取一点F,使得：DF = BD .则AD是BF的垂直平分线,可得：AB = AF ,∠AFB = ∠B = 2∠C .因为,∠FAC = ∠AFB-∠C = ∠C ,所以,CF = AF = AB ,可得：AB+BD = CF+DF = ...