令t=根号(1-x^2), dt = -x/根号(1-x^2) dx1+x^2 = 2-t^2原来积分变为-dt /(2-t^2)=根号2/4[1/(t+根号2) - 1/(t-根号2)]积分得到根号2/4 ln(t+根号2)(t-根号2) +C=根号2/4 ln (t^2-2) +C
