sin(-19π/6)/(sec4π/3)+tan7π/4=

已知α=π/24,求sinα(sec4αsec3α+sec3αsec2α+sec2αsecα+secα)=? 已知sin(x+π/6)=1/3,求sin(5π/6-x)+sin^2(π/3-x) 已知 cos π/5 =(根号5 +1）/4 求 sin π/5,sin -π/5 ,sin 4π/5 ,sin 3π/ 已知函数f(x)=cos(2x-π/3）+2sin(x-π/4）sin(x+π/4)=sin(2x-π/6) , 已知sinα（x+π/6）=1/4,则sin（5π/6-x）+sin（π/3-x）的平方=? α属于（0,π/2）且2sin²α-sinαcosα-3cos²α=0求sin(α+π/4)/sin 化简:sin(π/4-α)cos(π/3-α)-cos(π/6+α)sin(π/4+α)= 已知cos（α-π/6）+sinα=4/5 根号3,则sin(α+7/6π)=? 已知cos(α-π/6)+sinα=(4倍根号3)/5,则sin(α+7π/6)= 已知sin(a+π/6)+cosa=4/5倍根号3,则sin(a+π/3)= 若sin（π3 若sin(π/6-a)=根号3/3,则sin(7π/6-a)=