I = 0.9
c = 0.15
Tm = 0.3
Reduced Equation 1° order:
I used three steps to RK2 and found:
Is that correct?
How do I find the analytical solution?
I don't know about the Range-Kutta part but as far as an analytical solution goes you've already taken the first step yourself.
This is a Linear First Order differential equation. You can, if you've ever covered linear first order ODE's, solve this for and then go from there.
The general solution is the sum of the general solution of the homogeneous equation
and a particular integral of the original equation, and a PI for this is .
To get the actual solution you now apply the initial conditions to the general solution.