(sinx+cosx)²=1+sin2x=1/25所以：sin2x=-24/253sin²x/2+2sinx/2cosx/2+cos²x/2=2sin²(x/2)+sinx+sin²(x/2)+cos²(x/2)=2sin²(x/2)+sinx+1=1-cosx+sinx+1=2+sinx-cosx(sinx-cosx)&...