已知sin(π/6-α)=a,则cos(2π/3-α)=

已知2sin(a/2)=cos(a/2),则sin(a+π/6)= 已知sin(π/6-α)=a,则cos(2π/3-α)= 已知cos(π/6-a)=1/3,则cos(5π/6+a)sin(2π/3-a=? 已知cos^2A+cosA=1,则sin^6A+sin^2A=? 设角a=-35π/6,则2sin(π+α)cos(π-α)-cos(π+α)/ 1+sin^2α+sin(π-α)-cos^2(π+α)sina=sin(-35π/6)=sin(-6π+π/6)=1/2 cosα=根号3/22sin(π＋α)cos(π-α)-cos(π+α)/ [1+sin^2α+sin(π-α)-cos^2(π+α)]=2（-sinα)(-cosα）+cosα/[1+sin² 已知sina+sin^2a=1,则cos^2a+cos^6a+cos^8a= 已知 sin a-cos a=1/2,则 sin^3 a-cos^3 a 已知sin a=2cos a 计算⑴（sinα+2cosα)/(5cosα-sinα) ⑵tan(α+π/4) 已知cos(a-π/6)=-1/3则sin(2π/3-a)=? 已知sin(π/3 -a)=1/4 则cos(7/6π+a)= 已知sin(π/3 -a)=1/2,则cos(π/6 +a)=? 已知cos(π/6-a)=2/3 则sin(a-2π/3)=? 已知tana=2,则[sin(π/2+a)-cos(π-a)]/[sin(π/2-a)-sin(π-a)]=? 已知sin(π/6-a)=根号3/3,则 cos(4π/3+a) 已知sin（π/6+a）=1/3则cos(π/3-a)的值 已知sin(a-π/3)=1/3,则cos(π/6+a)的值为? 已知sin(6/π+a)=1/3,则cos(π/3-a)的值是 已知sin(a-π/3)=1/3,则cos(a+π/6)等于