(1)证明:在△ACD与△ABE中,
∵∠A=∠A,∠ADC=∠AEB=90°,AB=AC,
∴△ACD≌△ABE(AAS),
∴AD=AE;
(2)在Rt△ADO与Rt△AEO中,
∵OA=OA,AD=AE,
∴△ADO≌△AEO(HL),
∴∠DAO=∠EAO,即OA是∠BAC的平分线,
又∵AB=AC,
∴OA⊥BC.
(1)证明:在△ACD与△ABE中,
∵∠A=∠A,∠ADC=∠AEB=90°,AB=AC,
∴△ACD≌△ABE(AAS),
∴AD=AE;
(2)在Rt△ADO与Rt△AEO中,
∵OA=OA,AD=AE,
∴△ADO≌△AEO(HL),
∴∠DAO=∠EAO,即OA是∠BAC的平分线,
又∵AB=AC,
∴OA⊥BC.