A.k₁+k₂＞0                                      B.k₁+k₂=0

C.k₁+k₂＜0                                      D.k₁+k₂可取任意实数

A.b＞0,d＜0,a＜c                                B.b＞0,d＜0,a＞c

C.b＜0,d＞0,a＞c                                D.b＜0,d＞0,a＜c

A.［π，π)                                       B.（，π）

C.［0，)∪［，π)                      D.［0，］［π，π）

A.1                     B.2                  C.3                         D.4

A.45°                  B.60°               C.120°                   D.135°