化简cosπ/9*cos2π/9*cos3π/9*cos4π/9

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化简cosπ/9*cos2π/9*cos3π/9*cos4π/9
化简cosπ/9*cos2π/9*cos3π/9*cos4π/9

化简cosπ/9*cos2π/9*cos3π/9*cos4π/9
k/k法
cosπ/9*cos2π/9*cos3π/9*cos4π/9
＝[(2sinπ/9 cosπ/9)*cos2π/9*cos3π/9*cos4π/9]/(2sinπ/9 )
=[(2sin2π/9 cos2π/9)*cos3π/9*cos4π/9]/(4sinπ/9 )
=[(2sin4π/9 cos4π/9)*cos3π/9]/(8sinπ/9 )
=(sin8π/9 cos3π/9)/(8sinπ/9 )
=(cosπ/3)/8
=1/16.

cosπ/9*cos2π/9*cos4π/9=? cosπ/9cos2π/9cos23π/9 化简cosπ/9*cos2π/9*cos3π/9*cos4π/9 化简cos2α+cos2(π/3+α)+cos2(π/3-α)化简cos²α+cos²（π/3+α）+cos²（π/3-α） 化简cosπ/5cos2π/5RT. 求COSπ/5*COS2π/5 cosπ/5×cos2π/5= COSπ/5乘以COS2π/5 cosπ/5×cos2π/5 cosπ/5cos2π/5 cosπ/5cos2π/5=? cos兀/9×cos2兀/9×cos(-23兀/9) 求cosπ/9*cos2π/9*cos3π/9*cos4π/9 cosπ/9cos2π/9cos3π/9cos4π/9= cosπ/5 - cos2π/5 怎样变成 cosπ/5 + cos2π/5rt 求cosπ/9*cos2π/9*cos4π/9的值如题 cosπ/9*cos2π/9*cos4π/9怎么算的? 急 、COSπ/9*COS2π/9*COS4π/9=?同样,