cos（-7/6）∏=

cos（-7/6）∏= cos (2 a/7）+cos(4 a/7)+cos(6 a/7)=? cos（-19/6∏）= cos(π/7) + cos(6π/7) =几 请教关于用Matlab在非线性约束条件下的最优解在以下约束条件下cos(5*x)+cos(5*y)+cos(5*z)+cos(5*m)=0;cos(7*x)+cos(7*y)+cos(7*z)+cos(7*m)=0;cos(11*x)+cos(11*y)+cos(11*z)+cos(11*m)=0;使M=cos(x)+cos(y)+cos(z)+cos(m）最大的求 cos 2π/7 +cos 4π/7 +cos 6π/7=? 请问cos(2π/7)+cos(4π/7)+cos(6π/7)=?, cos(2派/7)+cos(4派/7)+cos(6派/7)=? cos(2π/7)+cos(4π/7)+cos(6π/7)= -1/2.证明[cos(2π/7)]^2+[cos(4π/7)]^2+[cos(6π/7)]^2=5/4 cos(2π/7)+cos(4π/7)+cos(6π/7)= -1/2.证明[cos(2π/7)]^2+[cos(4π/7)]^2+[cos(6π/7)]^2=5/4 求数学高手帮忙cos(2π/7)+cos(4π/7))+cos(6π/7)=?(化简求值) α,β为锐角,且cosα=1/7,cos(α+β）=-（11/14),cosβ=? 若f（sin x+cos x）=sin x·cos x,则f（cos 派/6）=? cos(7/6)TT=? 要过程 cos(-17/6π）= sin（sin（sin（sin（x）=cos（cos（cos（cos（x）,X等于多少? cos(pai/15)×cos(2pai/15)×cos(3pai/15)×cos(4pai/15)×cos(5pai/15)×cos(6pai/15)×cos(7pai/15)求值 cos(pai/15)×cos(2pai/15)×cos(3pai/15)×cos(4pai/15)×cos(5pai/15)×cos(6pai/15)×cos(7pai/15)求值