Thank you for your reply.
I have made the changes
DPICMR_R := diff(eval(ICMR, r(t) = rt), rt);
evalf(eval(DPICMR_R, [r(t) = 0.0024, z(t) = 0.001]));
When performing the calculation I get integrals.
The work I am doing is calculating the trajectory of a particle due to a magnetic force (Fm) and a fluidic force (Ff). Therefore, I have to calculate the trajectories r (t) and z (t) with the following expressions.
The Ff is easy to calculate but the Fm is difficult and I can't.
To calculate the Fm I have to know the MAGNETIC FIELD INTENSITY IN THE AXIS r (ICMR) and the MAGNETIC FIELD INTENSITY IN THE AXIS z (ICMZ) and their partial derivatives.
When I calculate the trajectories it gives me an error "you cannot calculate derivatives with integrals"
I attach a file with the work