已知sinx+siny=2sin(x+y)≠0,则tanx／2tany／2等于 是三角函数和差化积部分的

证明sin(x+y)sin(x-y)=sinx-siny 已知(sinx)2-(siny)2=m求sin(x y)sin(x-y)求sin(x+y)sin(x-y) 证明 [sin(2x+y)/sinx]-2cos(x+y)=siny/sinx 求证sin（2x+y)/sinx-2cos(x+y)=siny/sinx 求证：sin(2x+y)/sinx-2cos(x+y)=siny/sinx 已知sinx-siny=1/2,cosx-cosy=1/2,x、y均为锐角,求sin(x-y) 证明sin(x+y)sin(x-y)=（sinx）^2-(siny）^2. 求证：sin(2x+y)/sinx-2cos(x+y)=siny/sinx(2)已知5siny=sin(2x+y),求证:tan(x+y)=3/2 tanx 证明sinx+cos(x+y)siny/cosx-sin(x+y)siny=tan(x+y) 证明cosx(cosx-cosy)+sinx(sinx-siny)=2sin(x-y)/2 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 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 请问,如何证明sinx+siny=2*sin(x+y/2)*cos(x-y/2) 为什么sin（x+y) - sinx = 2cos(x+y/2)siny/2 求推导sinx-siny=2cos（(x+y)/2)sin((x-y)/2) 求证sinx+siny=2sin(x+y)/2*cos(x-y)/2