已知sinx+siny+sinz=0,cosx+cosy+cosz=0 则cos(x-y)=______ 要详解
已知sinx+siny+sinz=0,cosx+cosy+cosz=0 则cos(x-y)=______ 要详解
sinx+siny+sinz=0;cosx+cosy+cosz=0;求cos(x-y)
已知sinx+siny+sinz=0,cosx+cosy+cosz=0,求证cos(x-y)=cos(y-z)=cos(
sinx+siny+sinz=0,cosx+cosy+cosz=0,求cos(y-z)的值.
已知sinx+siny+sinz=cosx+cosy+cosz=0,求tan(x+y+z)+tanxtanytanz的值
已知x,y,z均为锐角,且sinx+sinz=siny,cosx-cosz=cosy,求x-y的值.
已知sinx+siny=0.4,cosx+cosy=1.2,则cos(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)=?
若cos(x+y)cosy+sin(x+y)siny=0,则cosx=