cosπ/5=cos4π/5,

cosπ/5=cos4π/5, cosπ/5 +cos2π/5 +cos3π/5 +cos4π/5 =可以简写. 求值:arccos(cos4/5π)= cosπ/9*cos2π/9*cos4π/9=? cosπ/7cos2/7πcos4/7π= 求cosπ/5乘cos2π/5乘cos3π/5乘cos4π/5 求值cosπ/5cos2π/5cos4π/5cos8π/5 sin5π/4cos4π/5tan11π/6sin乘cos乘tan cos4π=? -cos4/5π 是多少?用分式表示 比较cos4,cos4π/5,sin7/6π大小,大哥大姐们,帮帮俺啦. 比较cos4,cos4π/5,sin7π/6的大小如题 谢谢了 已知sin4次方-cos4次方=5/9,求cos4 cosπ/17cos2π/17cos4π/17cos8π/17=___ cosπ/7cos2π/7cos4π/7cos8π/7=?每步都写 cosπ/9cos2π/9cos3π/9cos4π/9= 急 、COSπ/9*COS2π/9*COS4π/9=?同样, cosπ/7cos2π/7cos4π/7=?写下过程,谢谢~