Question

在△ABC中,AB = AC,BD⊥AC于D求证：∠BAC = 2∠DBC

Answer 1

证明：∵AB = AC,∴∠ABC =∠C,∵BD⊥交流,∴RT⊿DBC,有：∠DBC = 90?稀释眺,⊿ABC,∠BAC = 180?/ B>∠ABC,∠C = 180?∠C = 2（90?稀条）,∴∠BAC = 2∠DBC.