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sinX=1/3 ,cos(2X - π)=
人气:168 ℃ 时间:2020-04-02 21:14:34
解答
cos(2x- π)= cos 2(x-π/2)=2*【cos(x-π/2) 】^2 -1 = 2 * (sin x )^2 -1 = - 7/9.
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