计算：cos（π/5)+cos（2π/5)+cos(3π/5)+cos(4π/5)

计算：cos（π/5)+cos（2π/5)+cos(3π/5)+cos(4π/5) 计算cos(π/5)cos(2π/5)的值 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)=? 计算∫[-2/π,2/π]cos^5dx 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 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) cos（π/11）cos（2π/11）cos（3π/11）cos（4π/11）cos（5π/11）怎么解 计算cos平方π/12-1/2 Cos[π/7] + Cos[2 π/7] + Cos[3 π/7] + Cos[4 π/7] + Cos[5 π/7] + Cos[6 π/7] + Cos[7π/7]过程思路 不要只有答案哦 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) 已知tan（α+π/4）=3,计算2sinαcosα+6cos方α-3/5cos方α-6sinαcosα-5sin方α