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已知sin(x+π/6)=1/3,求sin(7π/6+x)+cos²(5π/6-x)的值
明天要交了啊
人气:445 ℃ 时间:2020-02-06 06:27:05
解答
sin(7π/6+x)
=sin(π+π/6+x)
=-sin(π/6+x)
=-1/3
cos²(5π/6-x)
=1-sin²(5π/6-x)
=1-sin²[π-(5π/6-x)]
=1-sin²(π/6+x)
=8/9
所以原式=5/9
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