已知sin( θ-15° )=3/5,90° < θ<270° ,求cos(2 θ+15° )的值

已知sin( θ-15° )=3/5,90° < θ<270° ,求cos(2 θ+15° )的值 已知0<A<π/2<B<π,cos(B-π/4)=1/3,sin(A+B)=4/5求cos(a+ 已知sin(π/4--x)=5/13,0<x<π/4,求sin2π/cos(π/4--x)的值 已知√3sinα-cosα=4m-6（0<α<π）,求m的取值范围 已知tan@<0 cos@=-3/5 求sin@ tan@ 已知tan@<0 cos@=-5/3 求sin@ tan@ 已知sin[(π/4)-x)]=5/13,0<x<π/4.求cos2x/(cosπ/4+ (已知0<α<π,tanα=-2) 求2sin²α-sinαcosα+cos²α 求老师 已知π/4<a<b<π/2,且sin(a+b)=4/5,cos(a-b)=12/13 已知tan2x=-2 π/2<2x<π求[2cos^2(x/2)-sinx-1]/根号2sin(π/4+x) 已知tan(a+π/4)=-1/2,π/2<a<π,求(sin2a-2cos^2a)/√2sin(a-π/4 已知0<θ<π/2,0< φ<π/2则θ-φ等于多少度