2008/6/8 Ronald Modesitt <rmodesi at msn.com>:
> All,
>
> This is really more a Maxima procedure question than one about implicit
> differentiation. I would like to solve for d^2y/dx^2 ind the following
> equation.
>
>
>
> (%i1) eqn:x^2+y^2=r^2;
>
> (%o1) y^2+x^2=r^2
>
>
>
> (%i2) depends(y,x);
>
> (%o2) [y(x)]
>
>
>
> (%i3) d1:diff(eqn,x);
>
> (%o3) 2*y*('diff(y,x,1))+2*x=0
>
>
>
> (%i4) solve(d1,'diff(y,x));
>
> (%o4) ['diff(y,x,1)=-x/y]
>
>
>
> (%i5) d2:diff(eqn,x,2);
>
> (%o5) 2*y*('diff(y,x,2))+2*('diff(y,x,1))^2+2=0
>
>
>
> (%i6) subst(%o4,'diff(y,x),%o5);
You should do subst(%o4, %o5) here.
HTH,
--
Andrej