cos(-79/6∏)=?cos(-79/6∏)=(∏+12∏+1/6∏)＝继续写,别把上面的合了,就这样接下来写

cos(-79兀/6) cos cos(-79π/6)的计算过程 tan(-2010°)+cos(-79π/6) cos（-19/6∏）= cos（-7/6）∏= 1+cos(2θ)+cos(4θ)+cos(6θ)=4cosθcos(2θ)cos(3θ)证明相等. 化简cos(π/6a)+cos(π／6-a)= cos(π/7) + cos(6π/7) =几 cos²兀/6= cos(-19/6π)=? cos(-19／6n)= 若sinα+cosβ=2/3 cosα+cosβ=5/6求cos(α-β) sinα+cosα=1,求cos^2α+cos^6α+cos^8α的值. 化简(1-sin^6 a-cos^6 a)/(cos^2 a-cos^4 a)== Sina+sin^2a=1,cos^2a+cos^s4a+cos^6a cos 2π/7 +cos 4π/7 +cos 6π/7=? 请问cos(2π/7)+cos(4π/7)+cos(6π/7)=?,