Markus Nentwig - 2000-09-10

Question: How do I solve ordinary differential equations, possibly by using ATVALUE?

Answer:

(ID:1) diff(f(x),x)=3*f(x)
(ID:2 M) desolve(@1@,f(x))

results in
f(x)=F(0)*exp(3*x).

To get rid of the F(0), put an ATVALUE statement into the header. To do this, press F2, scroll to the bottom and add a line
atvalue(f(x),x=0,C0);
This tells Maxima, that f(0) equals C0.

Now re-evaluate command (2), and you get f(x)=C0*exp(3*x).

The same works with derivatives: atvalue(diff(f(x),...

The disadvantage to put it into the header is, that the ATVALUE statement is now 'visible' for any command on the sheet.
A slightly inofficial workaround is to use a list as a command:

(ID:3 M) [atvalue(f(x),x=0,C0),desolve(@1@,f(x))]