参考答案练测(13)1.A2.D3.C4.A5.B6.D7.C8.D9.C10.C11.若则12.()13.垂直相交14.15.5或16.用判定定理17.(1)(2)18.19.略20.(1)(2)(3)-2练测(19)1.B2.D3.B4.D5.D6.C7.C8.C9.C10.B11.C12.C13.1814.15.16.17.18.19.20.(1)略(2)21.(1)略(2)(3)略(4)1练测(20)1.C2.B3.A4.B5.B6.C7.A8.C9.A10.B11.B12.A13.14.②④15.216.17.略18.750或165019.20.∶21.练测(21)1---5DADAB6----10DDBCA11-----12AD13.无数条1415.17:716.17.2:118.略19.(1)略(2)20.300或60021.S练测(29)1.B2.D3.D4.C5.D6.A7.B8.D9.B10.A11.D12.A13.14.17915.12016.12017.(1)(2)18.144020.560x2,21.1722.(1)36(2)12(3)24(4)8练测(33)1.C2.C3.A4.C5.C6.D7.D8.C9.B10.B11.C12.B13.14.15.0.9916.0.9917.18.19.(1)0.97(2)0.0320.921.0.48822.(1)0.476(2)0.407(3)0.108(4)0.009