Two functions in mathcad

Hello Mathcad users,

I have a problem and I need help.

Suppose that I have two dependent functions u1(t) and Rm1(t) (see file attached, in yellow box).

The relation between them is in a loop.

I would like to plot both functions, but I don't know how to define these two functions at the same time: I tried with f(u1(t),Rm1(t)):=...,  but I cannot plot u1(t), Rm1(t).

Could you please help me to know how to define the two functions?

Thank you very much.

Son