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Cos四分之九派是等于

cos(9π/4) =cos(π/4) =√2/2

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

cos(-59π/17) =cos【(9-68)π/17)】 =cos(-4π+9π/17) =cos(9π/17) π/2

根据诱导公式cos(π-α)=-cosα就行

都cos了,怎么能是度呢?结果就是个值啊

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