已知cos(x-y)cosx+sin(x+y)sinx=m.且y为第三象限角,求siny?
已知sinx+siny=1/3,cosx-cosy=1/5,求cos(x+y),sin(x-y).
已知sinα+sinX+sinY=0,cosα+cosX+cosY=0,则cos(X-Y) 求思路过程.跪谢
已知sinx-siny=1/2,cosx-cosy=1/2,x、y均为锐角,求sin(x-y)
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cosx+cosy=1/2,sinx-siny=1/3,求cos(x+y)
求证:sin(x-y)/(sinx-siny)=cos[(x-y)/2]/cos[(x+y)/2]
cos(x+y)sinx-sin(x+y)cosx
已知sinx-siny=-2/3,cosx-cosy=2/3,且x.y为锐角,则tan(x-y)的值为?
已知sinx*siny=1,求cos(x-y)的值
已知sinx-siny=-23,cosx-cosy=23且x,y为锐角,则tan(x-y)= ___ .
已知sinx+siny+sinz=0,cosx+cosy+cosz=0 则cos(x-y)=______ 要详解