cos(α +2π/3)=1/6,则cos(2α-2π/3)
已知cosα=1/3,α属于(π,2π),则cosπ/2等于
已知cos(π\3-2)=1\3,则cosα+根号3sinα=
求和:cos(0)+cos(α)+cos(2α)+cos(3α)+……cos(nα)
cos(2π/3-α)能等于cosα?
【紧急求助】计算:cosα+cos(2π/3 +α)+cos(4π/3 +α)
若cos(α-3π/2)=1/5,求-cosα的值.
三角函数题2sin^2α-cos^α+sinα*cosα-6sinα+3cosα=0 求(2cos^α+2sinαcos
(1+sinα+cosα)*[sin(α/2)-cos(α/2)]/√(2+2cosα)化简 (3/2*π
已知3sinα=cosα,则sinα-2sinαcosα+3cosα+1=
已知(sinα-cosα)/(sinα+cosα)=1/3,则cos^4(π/3+α)-cos^4(π/6-α)的值为
cos^2(π/3-a)+cos^2(π/6+a)
cos(-2/3)π=?