(sinx-siny)(sinx+siny)-(cosx+cosy)(cosx-cosy)等於?

|sinx-siny| 证明sin(x+y)sin(x-y)=sinx-siny 证明不等式|siny-sinx| 为什么sinx*cosy-cosx*siny=sin(x-y) 求函数z=sinx+siny+sin(x+y)(0 存在sin( x -y) = sinX-sinY吗 sinx siny-sin(x y)如何化简 证明sinx+cos(x+y)siny/cosx-sin(x+y)siny=tan(x+y) 证明 [sin(2x+y)/sinx]-2cos(x+y)=siny/sinx 求证sin（2x+y)/sinx-2cos(x+y)=siny/sinx 证明cosx(cosx-cosy)+sinx(sinx-siny)=2sin(x-y)/2 求证：sin(2x+y)/sinx-2cos(x+y)=siny/sinx (sinx-siny)(sinx+siny)-(cosx+cosy)(cosx-cosy)等於? 已知sinx+siny=1/3,sinx-siny的最小值已知sinx+siny=1/3,sinx-已知sinx+siny=1/3,sinx-siny的最小值是 证明sin(x+y)sin(x-y)=（sinx）^2-(siny）^2. arcsin(sinx+siny)+arc(sinx-siny)=kπ/2,K为奇数,求sin^2x+sin^2y的值 三角不等式证明证明sin(x+y)+sin(y+z)+sin(z+x)>sinx+siny+sinz+sin(x+y+z) 请问,如何证明sinx+siny=2*sin(x+y/2)*cos(x-y/2)