> restart:
> #phi:=1/(2*Pi)^(n/2)*exp(-t/2);
> #g(u^2):=subs(t=u^2,phi);
> l:=log(g(u^2));
> map(factor,collect(diff(l,u$1),u));
> map(factor,collect(diff(l,u$2),u));

                                       2
                            l := ln(g(u ))


                                     2
                             2 D(g)(u ) u
                             ------------
                                   2
                                g(u )


              (2)      2     2          2 2   2           2
         4 ((D   )(g)(u ) g(u ) - D(g)(u ) ) u    2 D(g)(u )
         -------------------------------------- + ----------
                            2 2                        2
                         g(u )                      g(u )

> subs(t=u^2,2*diff(phi,t)/phi);

                                  -1

> diff(phi,t)/phi;
> 

                                 -1/2

> 
