change of time in ode45

May I ask how to code the change of time shown in picture in ode45 because normally was coded as t only in ode45 but this time the equations have different in time and I was unable to find any example online.

Thank you for the help.

Answer 1

[Steven Lord]

If the right hand side of your system of differential equations involves the solution at a previous time you don't have a system of ordinary differential equations you have a system of delay differential equations. See this documentation page for a discussion of the tools available for solving DDEs.

[Wei Qi Lim]

Above is part of my eq. Does that mean that my eq need to solve by DDEs not ODE45?