已知x-y=3/π且cosx-cosy=1/3,则cos(x+y)等于多少
已知x-y=3/π且cosx-cosy=1/3,则cos(x+y)等于多少
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cosx+cosy=1/2,sinx-siny=1/3,求cos(x+y)
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
cosx+cosy=1/2,sinx-siny=1/3,则cos(x+y)=?
已知sinx-siny=-1/3,cosx-cosy=1/2,求COS(X—Y)=
若cosx*cosy+sinx*siny=1/3 ,则cos(2x-2y)=?
已知x,y是实数且满足sinx*cosy=1,则cos(x+y)=
若sinx-siny=-1/3,cosx-cosy=1/2,则cos(x-y)=?
已知sinx+siny=1/2,cosx+cosy=1/3,求cos²((x-y)/2)