存在x,使得sin(x-y)=sinx-xiny,求证明

证明sin(x+y)sin(x-y)=sinx-siny 证明sinx+siny+sinz-sin(x+y+z)=4sin((x+y)/2)sin((x+y)/2)sin((x+ 证明：存在实数X,使得SIN x+cos X=60° 证明y=sinx+sinπx不是周期函数 证明 [sin(2x+y)/sinx]-2cos(x+y)=siny/sinx 证明sin(x+y)sin(x-y)=（sinx）^2-(siny）^2. 设y=sinx²+sin²x,求y' 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) 证明cosx(cosx-cosy)+sinx(sinx-siny)=2sin(x-y)/2 sin(x+y)-sinx=2cos(x+1/2y）sin(1/2y)的详细证明步骤. 求函数z=sinx+siny+sin(x+y)(0