cos(75°+α)=13
cos(75°+α)=13
已知cos(75°+α)=13,则cos(30°-2α)的值为 ___ .
已知cos(75°+α)=13
cos(75°+α)=1/3 则cos(150°-α)等于几.急……
已知cos(75°+α)=1/3,则cos(150°-α)的值是多少?
求证cos(720°+α)(2/cosα+tanα)(1/cosα-2tanα)=2cosα-3tanα
sinα+cosβ=sin225° sinα-cosβ=cos225°求cos(α-β)及cos(α+β)
若cosα=13
cos²α+cos²(120°-α)+cosαcos(120°-α)化简
sinα+sinβ=sinγ cosα+cosβ=cosγ 证明cos(α-γ)
化简cosα+cos(120°-α)+cos(120+α)
已知3sinα-2cosα=0,求(cosα-sinα)/(cosα+sinα)+(cosα+sinα)/(cosα-s