题目内容
已知x,y为锐角,且满足cos x=

A.

B.

C.

D.

【答案】分析:依题意求出sinx的值,通过cos(x+y)=
,求出sin(x+y)的值,然后利用y=x+y-x的关系求解sin y的值.
解答:解:已知x,y为锐角,且满足cos x=
,sinx=
;cos(x+y)=
,sin(x+y)=
sin y=sim(x+y-x)=sin(x+y)cosx-cos(x+y)sinx=
故选C
点评:本题考查两角和与差的正弦函数,考查计算能力,其中角的变换技巧y=x+y-x是解题关键,注意三角函数象限符号,本题是基础题.

解答:解:已知x,y为锐角,且满足cos x=




sin y=sim(x+y-x)=sin(x+y)cosx-cos(x+y)sinx=

故选C
点评:本题考查两角和与差的正弦函数,考查计算能力,其中角的变换技巧y=x+y-x是解题关键,注意三角函数象限符号,本题是基础题.

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