cos2a/sin(a-π/4) =-根号（2）/2,则cosa+sina的值为?

已知Sin(a+π/4)/cos2a=二分之根6求sin2a 证明：2sin(π/4+a)sin(π/4-a)=cos2a 求证：2sin(π/4+a)sin(π/4-a)=cos2a sin(π/4+a)sin(π/4-a)=1/6求cos2a tan(a+π/4)=2,则cos2a+3sin^2a+tan a= 已知sin（a-π）=3/5,求cos2a sin(a-π)=3/5求cos2a的值 已知cos2a=1/4,则sin^2 a=? 已知cos2a=1/4,则sin^2 a= 已知sin（π/4+a）+cos（π/4-a）=1/5,则cos2a 已知cos2a=4/5,且a属于[2分之π,π],则sin a=? a属于(0,π/2),sin^2a+cos2a=1/4,则tana= a是第四象限的角,cosa=5/13,sin(a+π/4)/cos2a=? tan(a+π/4)=2,则cos2a+3sin^2a+tan2a= 已知tan(a+π/4)=2 求cos2a+3sin²a得值 已知tan(a+π/4)=2,求cos2a+3sin²a的值 若sin(a-π/4)/cos2a=-根号2,则sina+cosa= cos2a/sin(a-π/4) =-根号（2）/2,则cosa+sina的值为?