已知0<A<π/2<B<π,cos(B-π/4)=1/3,sin(A+B)=4/5求cos(a+
已知0<A<π/2<B<π,cos(B-π/4)=1/3,sin(A+B)=4/5求cos(a+
已知π/4<a<b<π/2,且sin(a+b)=4/5,cos(a-b)=12/13
已知tan(a+π/4)=-1/2,π/2<a<π,求(sin2a-2cos^2a)/√2sin(a-π/4
已知sin[(π/4)-x)]=5/13,0<x<π/4.求cos2x/(cosπ/4+
已知A={x|a-4<x<2a+4},B={x|log2(x+2)《3}
一道关于向量的数学题已知向量a的模=2,向量b的模=4<a,b>=2/3π求<a,a-b>的余弦
已知sin(π/4--x)=5/13,0<x<π/4,求sin2π/cos(π/4--x)的值
已知tan2x=-2 π/2<2x<π求[2cos^2(x/2)-sinx-1]/根号2sin(π/4+x)
已知√3sinα-cosα=4m-6(0<α<π),求m的取值范围
当a>0,b>0时,2/(1/a+1/b)<=根号ab<=(a+b)<=根号[(a^2+b
(已知0<α<π,tanα=-2) 求2sin²α-sinαcosα+cos²α 求老师
已知全集I=R,集合A={x丨-2<x<3},B={x丨x<-4或x>2},C={x丨3a<