y=sinx+cosx=√2[sinx*(√2/2)+cosx*(√2/2)]=√2[sinx*cos(π/4)+cosx*cos(π/4)]=√2sin(x+π/4)∴ 周期是T=2πy=sinxcosx=(1/2)sin(2x)∴ 周期是T=2π/2=π∴ 函数y=sinx+sinxcosx+cosx 的周期是π....