0<a<π/4.sin(π/4-a)=5/13.求cos2a/cos(π/4+a)
0<a<π/4.sin(π/4-a)=5/13.求cos2a/cos(π/4+a)
已知sin(π/4-a)=5/13(0<a<π/4),求cos(π/4+a)/cos2a
已知0<a<π/2,cos=3/5; ①求tan a的值;②求cos2a+sin((π/2)-a)的值
已知sin(π /4+a)=12/13,a∈(0,派/4),求cos(a-派/4)/cos2a,
已知sin(π/4-a)=5/13,a∈(0,π/4),求cos2a/cos(π/4+a)的值
已知sin(π/4-a)=5/13 a∈(0,π/4)求cos2a/cos(π/4+a)
化简[cos(4a-π/2)*sin(π/2-a)*cos2a]/[(1+cos2a)(1+cos4a)*cosa
已知sin a+cos a=1/3,a属于(π/2,π),求cos2a
0<a<派/4,sin(派/4-a)=5/13,求cos2a/cos(派/4+a)的值.
已知sin(π/4—a)=5/13,0<a<π/4,则cos2a等于多少?
求证sin^4a-cos^4a=-cos2a
化简sin^4a-cos^4a/cos2a