A.
B.
C.
D.
[单选题]A.4.05mB.3.60mC.1.80mD.2.40m
[单选题]A.B.C.D.
[单选题]切,则π的方程为( ).A.B.C.D.
[单选题]A.B.C.D.E.A、B、C、D都不正确