siny+sinxcos(x+y)=siny+sinx(cosxcosy-sinxsiny)=siny+sinxcosxcosy-siny*(sinx)^2=siny[1-(sinx)^2]+sinxcosxcosy=sinycosx^2+sinxcosxcosy=cosx(sinycosx+sinxcosy)=cosxsin(x+y)同理,计算可以得到cosy-sinxsin(x...