> 数学 >
sin515°•cos35°-cos25°•cos235°的值为(  )
A. -
3
2

B.
3
2

C.
1
2

D. -
1
2
人气:143 ℃ 时间:2020-10-02 00:04:51
解答
sin515°cos35°-cos25°cos235°
=sin25°cos35°+cos25°cos55°
=sin25°cos35°+cos25°sin35°
=sin(25°+35°)
=sin60°
=
3
2

故选:B.
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