cosx=1/3,cos(x+y)=-3/5,且x,y都是锐角,则cosy=,
已知sinx+siny=-0.5,cosx-cosy=0.5,且X.Y都是锐角,则tan(x-y)=
已知:x-y=120度,且cosx+cosy=1/3,则cos(x+y)=
高一数学 已知x-y=120度,且cosx+cosy=1/3,则cos(x+y)=?
已知x-y=3/π且cosx-cosy=1/3,则cos(x+y)等于多少
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=1/3,cosx-cosy=1/5,求cos(x+y),sin(x-y).
已知cos(x-y)cosx+sin(x-y)sinx=3/5,则cosy的值为
已知sinx-siny=-2/3,cosx-cosy=2/3,且x.y为锐角,则tan(x-y)的值为?
sinx+siny=3/5,cosx+cosy=4/5,求cos(x-y)
已知cosx+cosy=1/2,sinx-siny=1/3,求cos(x+y)
cosx-cosy=4/1,sinx-siny=3/1求cos(x-y)