化简[cos(4a-π/2）*sin(π/2-a)*cos2a]/[(1+cos2a)(1+cos4a)*cosa

化简[cos(4a-π/2）*sin(π/2-a)*cos2a]/[(1+cos2a)(1+cos4a)*cosa 三角比：[cos(4a-PAI/2)*sin(PAI/2-2a)]/[(1+cos2a)*(1+cos4a)] 化简:sin2a/sin(π+a)+cos2a+1/cosa 化简[2sin2a/(1+cos2a)]*(cos^2a/cos2a) 已知sin a+cos a=1/3,a属于（π/2,π）,求cos2a 三角函数证明题(1)3+cos4a-4cos2a=8sin~4次方 a(2)tanatanb/tan2a-tana + cos2A+cos(4π/3-2A）化简, cos2a/sin(a-π/4) =-根号（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等于多少? 若cos2a/sin((a-(π/4))=-(√2)/2,则cosa+sina的值为 若sin(a-π/4)/cos2a=-根号2,则sina+cosa=