how can i work with the derivative of the input of a system

i have this code:

function [xdot, udot]=pid_practica9_ejercicio3_ec_diferencial_prueba2(t,x)

Vp=5;
u=Vp*square(2*pi*t)+5;

udot = 1.776*0.05252*(u-x(1, :));%udot must be the derivative of this

xdot = [
        x(2, :);
        20*udot-10*x(1, :)-7*x(2, :);
       ];

%[t,x]=ode45('pid_practica9_ejercicio3_ec_diferencial_prueba2',[0,10],[0,0])
%plot(t, x(:, 1));

where udot must be the derivative of: 1.776*0.05252*(u-x(1, :))

how can i do it?