### 2.4 Differential equation

Approximated solution (Runge-Kutta 4 method) of an equation of the kind: ${x}^{\prime }\left(t\right)+i{y}^{\prime }\left(t\right)=f\left(t,x,y\right)$ with initial condition $x\left({t}_{0}\right)={x}_{0}$ and $y\left({t}_{0}\right)={y}_{0}$:

• Shortcut: Ctrl+E
• We give a name.
• we give a command like [ f(t,x,y), t0, x0+i*y0],
• we choose the representation mode: coordinates (x,y) or (t,x) or (t,y).
• Corresponding graphical command: Equadif (to be used in a User-defined type element).