（1）过点C作CD⊥x轴于D,∵OA⊥OB,CD⊥AD,△ABC为等腰直角三角形,∴∠AOB=∠CAB=∠ADC=90°且AC=BA,∴∠DAC+∠OAB=90°∠OBA+∠OAB=90°,∴∠DAC=∠OBA,在Rt△ACD与Rt△BAO中∵∠DAC＝∠OBA ∠ADC＝∠AOB AC＝BA ∴R...