cos(2π-45)=cos(-45)=cos(45)=二分之根二,这里算的不是cos135了嘛,2π-45应该是315了嘛

cos ^2 (180+45)=? cos(π/32)*cos(π/16)*cos(π/8)= sin(45/2)/cos(45/2)=? 为什么cos(θ-2π)=cosθ, sin(2x+45)=cos cos(-2/3)π=? cos^2 π/8+cos ^2 3π/8+ cos^2 5π/8+cos^2 7π/8=? cos 2π/7 +cos 4π/7 +cos 6π/7=? 请问cos(2π/7)+cos(4π/7)+cos(6π/7)=?, 为什么cos(n-1)π=cos(n+1)πcos(n-1)π=cos(n-1+2)π=cos(n+1)π 对吗? 三角函数周期x(t)=2+cos(πt+30)+2cos(2πt+45)+4cos(3πt+60)+8cos(6πt+90)求最小周期和谐波频率 cosπ/12= 计算：tan(45)sin(45)-2cos(30)cos(45)+tan(30)= 求证cos^2(A=45度)=COS^2(A-45度)=1 求证cos^2(A=45度)=COS^2(A-45度)=1 证明cos 2x cos x=1/2(cos x+cos 3x) cos^1度+cos^2度+cos^3度+……+cos^180度=? 求证cosα^2+cos(α+β)^2-2cosαcosβcos(α+β)=sinβ^2