题目内容
解析：原式=
=
=2cos.
答案：2cos
A.sin(-1) B.sin(+3 999)
C.cos(-1) D.cos(+3 999)
A.3-cos2x B.3-sin2x C.3+cos2x D.3+sin2x
(1)y=;(2)y=.
cosαcosβ=cos(α+β)+ _______________=cos(α-β)- _______________.
=____________________.
.
=____________________.=____________________..
+1 999)cos2 000-cos(
+1 999)sin2 000的结果是( )
-1) B.sin(
+3 999)
-1) D.cos(
+3 999)
.
，则sin2(x-
)的值等于__________________.
,tan(α-β)=-
,则cosβ=_________________.
;(2)y=
.
(1+tanx·tan
)=tanx.