[Maxima] how to solve for an implicit derivative --

Stavros Macrakis macrakis at alum.mit.edu
Tue Oct 21 11:06:50 CDT 2008


This seems to work fine for me:

(%i2) depends(y,x);
(%o2) [y(x)]
(%i3) diff(x^2+y^2-1,x);
(%o3) 2*y*'diff(y,x,1)+2*x
(%i4) solve(%,diff(y,x));
(%o4) ['diff(y,x,1) = -x/y]

Is this what you had in mind?

             -s


Comments on your code in-line:

On Tue, Oct 21, 2008 at 11:53 AM, <shorne at energetiq.com> wrote:

> f(x,y)=0;
> depends(y,x);
> eq1: diff(f,x);


You need to define f before taking the diff.
And you need to diff an *expression* (e.g. f(x,y)) not a named *function*
(e.g. f).

solve(eq1, dy/dx);
>

dy/dx is expressed as 'diff(y,x) == diff(y,x)
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