sin(π/4+a)sin(π/4-a)=1/6求cos2a
已知Sin(a+π/4)/cos2a=二分之根6求sin2a
求证:2sin(π/4+a)sin(π/4-a)=cos2a
证明:2sin(π/4+a)sin(π/4-a)=cos2a
若a∈(0,π/2)且sin^2 a+cos2a=1/4,求tan a的值
若 cos2a/sin(a-π/4)= -√2/2,求cosa+sina的值.
已知tana+cota=5/2,求cos2a和sin(2a+π/4)
已知sin a+cos a=1/3,a属于(π/2,π),求cos2a
已知cos2a=(1/4),求cos^4a+sin^4+sin^2acos^2a的值
已知sin(π /4+a)=12/13,a∈(0,派/4),求cos(a-派/4)/cos2a,
求证:sin a (1+cos2a)=sin a cos a
化简[cos(4a-π/2)*sin(π/2-a)*cos2a]/[(1+cos2a)(1+cos4a)*cosa
求证sin^4a-cos^4a=-cos2a