f(x＋a)=f(x＋3a)sin(x＋a)＋cos(x＋a)=sin(x＋3a)＋cos(x＋3a)sin(x＋a)－sin(x＋3a)=cos(x＋3a)－cos(x＋a)2cos(x＋2a)sin(－a)=－2sin(x＋2a)sin(a)sina[cos(x＋2a)－sin(x＋2a)]=0sina=0,因a属于(0,π/2),则不存...