cosθ+cos(120°-θ)+cos(120°+θ)怎么化简,急用,
cos²α+cos²(120°-α)+cosαcos(120°-α)化简
化简cosα+cos(120°-α)+cos(120+α)
cos^2x+cos^2(x+120°)+cos^2(x+240°)
(sinθcosπ/3)-(cosθsinπ/3)怎么化简得sin(θ-π/3)
化简cos^2A+cos^(120°+A)+cos^2(240°+A)这个怎么化简呢?
sin(θ+75°)+cos(θ+45°)-3cos(θ+15°
2cos³θ+sin²(360°-θ)+cos(360°-θ)-3/2+2cos²(180°-θ)+cos(-θ)怎样化
|cosθ|=-cosθ,tanθ
sinΘ-2cosΘ=0,Θ属于(0.,90°),求sinΘ、cosΘ的值.
化简cos平方(θ+15°)+cos平方(θ-15°)-(√3/2)cos2θ
怎样化简cosαcos(60°-α)+1
求证:(1+cosθ+cosθ/2) /(sinθ+sinθ/2)=sinθ/1-cosθ