> 数学 >
已知sin(x+
π
12
)=
1
3
,则cos(x+
12
)
的值为(  )
A.
1
3

B. -
1
3

C. -
2
2
3

D.
2
2
3
人气:494 ℃ 时间:2020-02-05 16:02:57
解答
sin(x+
π
12
)=
1
3
,∴cos(x+
12
)
=cos[
π
2
+(x+
π
12
)]
=-sin(x+
π
12
)
=-
1
3

故选B.
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