分部積分法.
I = ∫ ln(1+√x)dx = xln(1+√x) -(1/2) ∫ √x/(1+√x)dx
= xln(1+√x) - ∫ x/(1+√x)d√x
令 t=√x, 則I1= ∫ x/(1+√x)d√x = ∫ t^2dt/(1+t) = ∫ [t-1+1/(1+t)]dt = t^2/2-t+ln(1+t)-C
=x/2-√x+ln(1+√x)-C,
則 I = xln(1+√x)-x/2+√x-ln(1+√x)+C.