sin(x+y)-sinx=2cos(x+1/2y）sin(1/2y)的详细证明步骤.

sin(x+y)-sinx=2cos(x+1/2y）sin(1/2y)的详细证明步骤. 证明 [sin(2x+y)/sinx]-2cos(x+y)=siny/sinx 证明COS（X+Y）COS（X-Y）=COS^2X-SIN^2Y 请问,如何证明sinx+siny=2*sin(x+y/2)*cos(x-y/2) 请问怎么证明sinX+sin(X+Y)+sin(X+2Y)/cosX+cos(X+Y)+cos(X+2Y)=tan(X+ 证明sinx+siny+sinz-sin(x+y+z)=4sin((x+y)/2)sin((x+y)/2)sin((x+ 证明sin(x+y)sin(x-y)=（sinx）^2-(siny）^2. 求证：sin（x-y）/（sinx-siny）=cos[（x-y）/2]/cos[(x+y)/2] Sin x-sin y=2/3 cos x-cos y=1/2 求cos(x-y) 函数y=sin*2x+sinx-1的值域 求证：sin(2x+y)/sinx-2cos(x+y)=siny/sinx 一道关于数学三角函数的题,哪位数学好的朋友帮哈忙,谢 证明sin(x+y)-sinx=2cos((2x+y)\2)sin