已知cos（a-π/6)+sina=五分之四倍根号三,则cos(a+2π/3)的值是

已知sin二分之A-cos二分之A=五分之一,求sinA 已知[sina(a-π/4)]/cos(π+2a)=根号2,则sina+cosa=? 已知锐角a满足sina=4/5,则cos(π/6-a) 已知2sina/2·cos(π/2-a/2)=3/4,求sina 已知sina+sin^2a=1,则cos^2a+cos^6a+cos^8a= 已知sin a+cos a=1/2 sina*cosa=?cos a/sina+sina/cosa=? cos(a+π/6)=-4/5 sina=? cos(a-π/2)=sina cos(A-π/2)=-sinA 已知cos(a-π/6)=4/5 (π/6＜a＜2π/3)求sina的值 已知cos(a-π/6）+sina=4根号下3/5,则sin(a+7π/6)=? 已知cos（a-π/6）+sina=4√3/5,则sin(a+7π/6)=? 已知cos(a-π/6)+sina=(4*根号3)/5,则sin(a+7π/6)的值是( ) 已知cos(a-π/6)+sina=4√3/5,求sin(a+7π/6)的值为 已知2tana×sina=3,-π/2＜a＜0,则cos（a-π/6）= 已知:sina=2/3,求sin(2a+π/3)+cos(2a+π/6)的值 已知π/4已知sina=4根号3/7,cos(a-β),且0 已知sina=2/3 a∈(π/2,π) 求cos(π/3+a) cos(π/3-a)