Substituting variable/function
I got a problem with substituting a solution into another equation. I could break down my problem to a simple example:
r = var('r');
p = function('p')(r);
v = var('v');
v = p + p.derivative(r);
p1(r)=desolve(p.derivative(r)==0,p,ivar=r); p1(r)
v.subs(p(r)==p1)
Output:
_C
_C + diff(p(r), r)
What's happening here? Why is p substituted, but not diff(p,r)=0? What's the correct way to do this substitution?