用分部积分法,∫(x^2-2x+3) cos2x dx=∫ 0.5(x^2-2x+3) d(sin2x)=0.5(x^2-2x+3)*(sin2x) - ∫ 0.5(sin2x) d(x^2-2x+3)=0.5(x^2-2x+3)*(sin2x) - ∫ 0.5(sin2x)(2x-2) dx而∫ 0.5(sin2x)(2x-2) dx=∫ -0.5(x-1) d(cos...