cos兀/9×cos2兀/9×cos(-23兀/9)

cos兀/9×cos2兀/9×cos(-23兀/9) cos兀/9·cos2兀/9·cos（-23兀/9）=?怎么算? cos兀/7cos2兀/7cos3兀/7=? cosπ/9*cos2π/9*cos4π/9=? cosπ/9cos2π/9cos23π/9 sin@cos@cos2@ 已知cos(x+兀/6)=1/4,求cos(5兀/6-x)+cos2(兀/3-x)的值 化简:cos2α-cos2β/cosα-cosβ (cos2α-cos2β)/(cosα-cosβ) cos兀/7+cos2兀/7+……cos6兀/7 cos兀/5×cos2兀/5的值是多少（要过程） 化简cosπ/9*cos2π/9*cos3π/9*cos4π/9 求cosπ/9*cos2π/9*cos3π/9*cos4π/9 cosπ/9cos2π/9cos3π/9cos4π/9= 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, ⑴ 1+sin2θ-cos2θ/1+sin2θ+cos2θ ⑵已知 13sinα+5cosβ=9,13cosα+5sinβ=15 ,求cos(α+⑴ 1+sin2θ-cos2θ/1+sin2θ+cos2θ⑵已知 13sinα+5cosβ=9,13cosα+5sinβ=15 ,求cos(α+β)的值