设cosx+cosy=1/2,sinx+siny=1/4,求cos(x-y)的值
设cosX+cosY=1/2,sinX+sinY =1/4,求cos(X-Y)的值
设cosx+cosy=1/2,sinx+siny=1/4,求cos(x-y)的值
已知sinx+siny=(√2)/4,cosx+cosy=1/2,求cos(x-y)的值.
sinX+sinY=1 cosX+cosY=0 求cos(2X)+cos(2Y)的值
cosx-cosy=4/1,sinx-siny=3/1求cos(x-y)
已知cosx+cosy=1/2,sinx-siny=1/3,求cos(x+y)
设sinX+sinY=1/4,cosX+cosY=1/3,求tan(X+Y)的值.要详解.
sinx+siny=-1/3 cosx+cosy=1/2,求sin(x+y)的值.
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=1/2,cosx+cosy=1/3,求cos²((x-y)/2)
已知sinx-siny=-1/3,cosx-cosy=1/2,求COS(X—Y)=