计算cos(π/5)cos(2π/5)的值

计算cos(π/5)cos(2π/5)的值 计算：cos（π/5)+cos（2π/5)+cos(3π/5)+cos(4π/5) 计算cos(a+5π/12)cos(a+π/6)+cos(π/12-a)cos(π/3-a） 求值:cos(π/11)cos(2π/11)cos(3π/11)cos(4π/11)cos(5π/11) 求值：cos(π/11)-cos(2π/11)+cos(3π/11)-cos(4π/11)+cos(5π/11) cos(π/11)cos(2π/11)cos(3π/11)cos(4π/11)cos(5π/11) 计算cos(π/3+arcsin4/5)=? 三角函数求值(急)哪个高手帮忙求一下Cos(π/3)Cos(π2/3) 要计算出来的 不要查表的刚搞错了 不好意思 是Cos(π/5)Cos(π2/5) 计算∫[-2/π,2/π]cos^5dx cos (π/12) × cos(5×π/12)的值 cos^2 π/8+cos ^2 3π/8+ cos^2 5π/8+cos^2 7π/8=? [sin(5π-α)cos(-π-α)]/[cos(α-π)cos(π/2+α)]化简 cos(-A-11π/2) =cos(A+11π/2)怎样计算来的? 计算cosa+cos(2π/3+a)+cos(4π/3+a)的值 cosθ^2+cos(θ+2π/3)^2+cos(θ-2π/3)^2 计算 【紧急求助】计算:cosα+cos(2π/3 +α)+cos（4π/3 +α） 已知sin a=2cos a 计算⑴（sinα+2cosα)/(5cosα-sinα) ⑵tan(α+π/4) 三角函数计算的已知cos(a+π/4)=3/5,π/2≤a