∫盯空xsin(x^2+1)dx 因为d(x^2)=2xdx 所以上薯数面式子 =(1/凯手瞎2)*∫sin(x^2+1)d（x^2) =(1/2)*∫sin(x^2+1)d（x^2+1) =(1/2)*(-cos(x^2+1)) =-[cos(x^2+1)]/2
