sina=根号5／5则sin^4a-cos^4a=详细的问题说明,有助于回答者给出准确的答案

已知sina=根号5/5,则sin^4 a-cos^4 a [急!] 已知sina=根号5/5,则sin^4-cos^4a得值? 已知sinA=4/5,则co s A和sinA等于多少 sin (a+兀/3)+sina=-4根号3/5,求cos a-兀/2 COS(A-30度)+SINA=4/5 乘根号3 求SIN(A+210度)? 已知sina=根号5/5,则sin^4a-cos^4a的值为_____, 已知cos(a+兀/6)-sina=4/5根号3,则sin(a-兀/6)= 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*根号3)/5,则sin(a+7π/6)的值是( ) sin(a+π/3)+sina= - 4根号3/5,则cos(a+2π/3)怎么求》 已知sin(a+π/3)+sina=-(4倍根号下3)/5,-π/2 已知sin(a+π/3)+sina=-4根号3/5,-π/2 已知sin(a+pie/3)+sina=-4根号3/5,-pie/2 已知sin(a+π/3)+sina=-4根号3/5 -π/2 sina=根号5/5,sin(a-b)=-根号10/10.a,b均为锐角,则b= sin2a/sin(a-π/4)=-根号2/2,则sina+cosa=sin2a / sin(a-π/4)= - 根号2/2, 则sina+cosa= 已知sina=根号5/5,则sin四次方a-cons四次方a是值为 sina=5／4,那么sin（a+4／pi）-二／根号2•cos（pi-a）=