A.充分而不必要条件                    B.必要而不充分条件

C.充要条件                                D.既不充分也不必要条件

A.                                   B.

C.cos                              D.以上答案都不对

A.              B.               C.-               D.

A.arctan3                               B.arctan

C.±arctan                          D.π±arctan

(2)已知tan(-x)=-且x∈(,),求x.

(1)当x∈［0,π］时，x=_______________;

(2)当x∈［π,2π］时，x=_______________；

(3)当x∈［0,2π］时，x=_______________;

(4)当x∈R时，x=_______________.