sinx+siny+sinz=0,cosx+cosy+cosz=0,求cos（y-z）的值.

sinx+siny+sinz=0;cosx+cosy+cosz=0;求cos(x-y) 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（y-z）的值. 已知sinx+siny+sinz=0,cosx+cosy+cosz=0,求证cos(x-y)=cos(y-z)=cos(z-x) sinX+sinY+sinZ=0 同时满足cosX+cosY+cosZ=0求cos(X-Y)为何值?所有的条件就这些了,我只要答案, 1.已知8cos(2x+y)+5cosy=0,求tan(x+y)*tanx的值.2.已知关于x的方程x^2+px+q=0的两根是tanx,tany,求sin(x+y)/cos(x-y)的值.3.化简:sin(x-y)/(sinx*siny)+sin(y-z)/(siny*sinz)+sin(z-x)/(sinz*sinx). 已知sinx+siny+sinz=cosx+cosy+cosz=0,求tan(x+y+z)+tanxtanytanz的值 已知x,y,z属于(0,派/2),sin^2x+sin^2y+sin^2z=1,求(sinx+siny+sinz)/(cosx+cosy+cosz)的最大值 一道关于三角函数的不等式证明题已知0≤x＜y＜z≤π求证：（siny-sinx）/(y-x)>(sinz-siny)/(z-y) 已知sinx+siny=1/3,求 siny-cos²x的最大值? 证明sinx+cos(x+y)siny/cosx-sin(x+y)siny=tan(x+y) siny+sinx=1/3,则siny-cos²x的最大值为---,最小值为--- 已知sinx+siny=2/3,求2/3+siny-cos²a取值范围 已知sinx+siny=2/3,求2/3+siny-cos²a取值范围 sinX+sinY=1 cosX+cosY=0 求cos(2X)+cos(2Y)的值 m=(sinx)/sin(y-z),n=(siny)/sin（z－x）,p=（sinz）/sin（x－y）,求mn+np+pm. 已知x,y,z均为锐角,且sinx+sinz=siny,cosx-cosz=cosy,求x-y的值. 若sinx+sinz=2siny,求证:tan((x+y)/2)+tan((y+z)/2)=2tan((x+z)/2)