2022年九年级中考数学二轮复习专题：圆的有关概念与性质

= Z-A.\r *4 = 68°,\rZ.CED = 68°C\r( 2 ) ?\r? ? AE,\r DE = BE,\r@, DE = BE,\r1 i\rA Z-DAE = Z,EAB = -2Z .CAB = 2 x 68° = 34°,\rv A B \r`AEB = 90°,\rZ.AEC = 90°,\r  zC = 90° - Z.DAE = 90° - 34° = 56°.\r34 . P0`p\r( 1 ) ?\r? ? CD, OD.\rv /-CAB<=>&  '  D,\r Z-CAD = ` DAB,\rv `COD = 2`CAD, `DOB = 2/.DAB,\r:.`COD = `DOB,\r  CD = DB,\r# B C    \r Z.CDB = 90°,\r Rt # CDB \rCD2 + BD2 = BC2,\r  BD = 5V2.\r( 2 ) ?\r? ? OB, OD,\r??     10,\r:.OB = 0D = 5,\rv BD = 5,\r OB = OD = BD,\r8@9\r.\r:.BOD = 60°,\r4BAD =-Z2.BOD = 30°,\r: , ( CAB<=>&  '  D,\rZ.CAD = Z.BAD = 30°,\r Z.BAC = 60°,\r.:789ABDC  0 ;?789,\r Z-CDB = 180° - BAC = 120°.