已知sinx+siny=0.4,cosx+cosy=1.2,则cos(x-y)=______.
已知sinx+siny=0.4,cosx+cosy=1.2,则cos(x-y)=______.
已知sinx+siny+sinz=0,cosx+cosy+cosz=0 则cos(x-y)=______ 要详解
已知cosx+cosy=1/2,sinx-siny=1/3,求cos(x+y)
cosx+cosy=1/2,sinx-siny=1/3,则cos(x+y)=?
若cosx*cosy+sinx*siny=1/3 ,则cos(2x-2y)=?
已知sinx+siny=(√2)/4,cosx+cosy=1/2,求cos(x-y)的值.
已知sinx-siny=-1/3,cosx-cosy=1/2,求COS(X—Y)=
已知sinα+sinX+sinY=0,cosα+cosX+cosY=0,则cos(X-Y) 求思路过程.跪谢
若sinx-siny=-1/3,cosx-cosy=1/2,则cos(x-y)=?
已知sinx+siny=1/3,cosx-cosy=1/5,求cos(x+y),sin(x-y).
已知sinx+siny=1/2,cosx+cosy=1/3,求cos²((x-y)/2)
sinx+siny=2/5,cosx+cosy=6/5,求cos(2x-2y)