过点C作CD⊥x轴于点D，过点A作AE⊥y轴于点E，∴∠CDO=∠AEO=90°．∵四边形OABC是正方形，∴∠AOC=90°，OC=OA．∵∠DOE=90°，∴∠AOC=∠DOE，∴∠AOC-∠AOD=∠DOE-∠AOD，∴∠COD=∠AOE．在△CDO和△AEO中，∠CDO...