证明sinx+cos(x+y)siny/cosx-sin(x+y)siny=tan(x+y)

证明sin(x+y)sin(x-y)=sinx-siny 证明 [sin(2x+y)/sinx]-2cos(x+y)=siny/sinx 证明cosx(cosx-cosy)+sinx(sinx-siny)=2sin(x-y)/2 请问,如何证明sinx+siny=2*sin(x+y/2)*cos(x-y/2) 证明sin(x+y)=sinx*cosy+cosx*siny的过程 已知sinx+siny=1/3,cosx-cosy=1/5,求cos(x+y),sin(x-y). 求证：sin(2x+y)/sinx-2cos(x+y)=siny/sinx 证明sin(x+y)sin(x-y)=（sinx）^2-(siny）^2. 证明sinx+siny+sinz-sin(x+y+z)=4sin((x+y)/2)sin((x+y)/2)sin((x+ 证明|x-y|≥|sinx-siny| |sinx-siny|≤|x-y|如何证明 证明不等式|sinx-siny|《 |x-y|