(1)补充条件:AC=BD∵AD=BCAB=AB△ACB≌△BDA(2)补充条件:∠CBA=∠DAB∵AD=BCAB=AB△ACB≌△BDA(3)补充条件:OA=OB∠CBA=∠DAB∵AD=BCAB=AB△ACB≌△BDA