设1+x^2=t
dt=2xdx
即xdx=(1/2)dt
∫x√1+x^2 dx
=(1/2)∫t^(1/2)dt
=(1/2)*(2/3)*t^(3/2)
=(1/3)(1+x^2)^(3/2)
=(1/3)(1+x^2)√(1+x^2)
∫x√1+x^2 dx
=1/2∫√(1+x^2) d(1+x^2)
=1/2*2/3*(1+x^2) ^(3/2)+C
=1/3*(1+x^2) ^(3/2)+C
[(1+x^2)^(3/2)]'=3/2* 2*x√1+x^2 =3x√1+x^2
∫x√1+x^2 dx =1/3*∫1 d[(1+x^2)^(3/2)]x =[(1+x^2)^(3/2)]/3+c