若cos2a/sin(a-π/4)=-√2/2,则cosa+sina等于多少?

若cos2a/sin(a-π/4)=-√2/2,则cosa+sina等于多少? 若cos2a/sin((a-(π/4))=-(√2)/2,则cosa+sina的值为 若 cos2a/sin（a-π/4)= -√2/2,求cosa+sina的值. 若((cos2a)/(sin(a+(π/4))))=-√2/2则cosa-sina的值是 求值 三角函数若cos2a/sin（a-π/4）=-√2/2,则sina+cosa=? 若sin(π/2+a)=1/√3,则cos2a的值为? 若sin(a-π/4)/cos2a=-根号2,则sina+cosa= 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 已知sin(a+π/4)+sin(a-π/4)=√2/3则sin(a-π/4)/1-cos2a-sin2a的值 若a∈(π/2,π),3cos2a=sin(π/4-a),则sin2a的值 若a(0,π/2),且sin^2 a+cos2a=1/4 则tana的值等于 若a属于（0,π/2）,且sin²a+cos2a=1/4,则tana的值等于 cos2a=1-2sin²a 为什么又等于cos2a=-√[1-(sin2a)^2] tan(a+π/4)=2,则cos2a+3sin^2a+tan a= 若cos2a=a,则sin*4a+cos*4a=? 已知sin（a-π）=3/5,求cos2a