sin（x-y）=0sinxcosy- cosxsiny =0cos（x+y）=0cosxcosy-sinxsiny = 0sinxcosy- cosxsiny = cosxcosy-sinxsinysinx-cosxtany= cosx- sinxtanysinx-cosx= -tany(sinx-cosx)(sinx-cosx)(1-tany)=0sinx = cos xx = 2k...