1.若sinαsinβ+cosαcosβ＝0，那么sinαcosα+sinβcosβ的值等于(    )

A.-1            B.0             C.           D.1

2.(tan22.5°+cot22.5°)的值是(    )

A.7             B.          C.7         D.log₂7

3.函数f(x)＝cos2x+cos(x+)+sin(x+)+3sin²x的最小值是(    )

A.0             B.2             C.            D.3

4.已知log₂a＝b，则(cos15°sin15°)^b等于(    )

A.a²            B.            C.           D.a

5.若方程sec²x+2tanx-3＝0有两根α、β，则cot(α+β)＝(    )

A.-cot2         B.-           C.-           D.

6.已知sinθ+cosθ＝ (0＜θ＜π，则cos2θ的值为(    )

A.±            B.-         C.              D.-

7.已知cos78°约等于0.20，那么sin66°约等于(    )

A.0.92          B.0.85          C.0.88          D.0.95

8.若0＜2α＜90°＜β＜180°，a＝(sinα)^cosβ，b＝(cosα)^sinβ,c＝(cosα)^cosβ则(    )

A.a＞c＞b                       B.a＞b＞c

C.b＞a＞c                       D.c＞a＞b