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Cos四分之九派是等于

cos(9π/4) =cos(2π+π/4)=cos(π/4)=√2/2(相当于转了一个2π的周期)

是求值吗?若是这样,则方法如下: 原式=cos(2π/14)cos(4π/14)cos(6π/14) =2sin(2π/14)cos(2π/14)cos(4π/14)cos(6π/14)/[2sin(2π/14)] =sin(4π/14)cos(4π/14)cos(6π/14)/[2sin(π/7)] =2sin(4π/14)cos(4π/14...

如图即可

cos(x+π)=-cosx

已知cos阿尔法等于负四十一分之九,派<阿尔法<2派,求sin∂,tan∂,cot∂的值 sin∂=四十一分之四十 tan∂=负九分之四十 cot∂=负四十分之九

根据诱导公式cos(π-α)=-cosα就行

sin(5π/9)=sin(π-4π/9)=sin(4π/9) cos(5π/9)=cos(π-4π/9)=-cos(4π/9)

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