求证:2sin(π/4+a)sin(π/4-a)=cos2a
求证:2sin(π/4+a)sin(π/4-a)=cos2a
求证sin^4a-cos^4a=-cos2a
证明:2sin(π/4+a)sin(π/4-a)=cos2a
求证:sin a (1+cos2a)=sin a cos a
若sin(a-π/4)/cos2a=-根号2,则sina+cosa=
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
已知tana+cota=5/2,求cos2a和sin(2a+π/4)
cos2a/sin(a-π/4) =-根号(2)/2,则cosa+sina的值为?
2sin(4分之派+a)sin(4分之派-a)=cos2a
化简[cos(4a-π/2)*sin(π/2-a)*cos2a]/[(1+cos2a)(1+cos4a)*cosa