sinx^2+sinxcosx=(1-cos2x)/2 + sin2x/2 = (sin2x-cos2x)/2 + 1/2 = 2^(1/2)(2^(1/2)/2*sin2x - 2^(1/2)/2*cos2x) + 1/2=2^(1/2)(sin2x-pai/4) + 1/2最小正周期是2pai／2　＝　pai