cosx*cosy=1,sin(x+y)=?

cosx*cosy=1,sin(x+y)=? (cosx)^2-(cosy)^2=1/3求sin(x+y)*sin(x-y). 为什么sinx*cosy-cosx*siny=sin(x-y) cosx-cosy=1/2,sinx-siny=1/3,sin(x+y)=RT sinx+cosy=1/3 cosx+siny=1/6 则sin(x+y)=?RT sinx+cosy=1/3 cosx+siny=1/6 则 sin(x+y)? sinx+siny=-1/3 cosx+cosy=1/2,求sin(x+y)的值. sinx-siny=1/3,cosx-cosy=2/3,sin(x+y)=? sin（x+y）*sin（y-x）=m,cosx的平方-cosy的平方? 求证cosx-cosy=-2sin （x+y/2）*sin （x-y/2） 证明cosx(cosx-cosy)+sinx(sinx-siny)=2sin(x-y)/2 已知sinx+siny=1/3,cosx-cosy=1/5,求cos(x+y),sin(x-y).求过程! 已知sinx-siny=1/2,cosx-cosy=1/2,x、y均为锐角,求sin(x-y) 若cos(x+y)cosy+sin(x+y)siny=0,则cosx= 已知cosx+cosy=1/3 ,求cosx-sin^2y的最大值和最小值 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 sinx+siny=1/2,cosx+cosy=（根号3）/3,求sin[(x-y)/2] （COSx）^2--(COSy）^2=(根号3)/2,求SIN(X+Y).SIN(X-Y)=