How to plot the “Response” and the “damping exponential function of the transient solution” on the same figure?

how to plot the exponential curve like this pucture on the same figure ?

I have done this part of the code

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clear all;close all;

clc;

xss=0.01;

wf=40;

wn=20;

zeta=0.1;

A=0.1; B=0.04;

wd=wn*sqrt(1-zeta^2);

t=0:0.005:4;

X=xss*cos(wf*t)+(A*sin(wd*t)+B*cos(wd*t)).*exp(-zeta*wn*t);

plot(t,X,'r','LineWidth',2)

grid on

and i got this

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i need it like this

Answer 1

[Mathieu NOE]

hello

If you have the Signal Processing Tbx, envelope was made for you

clear all;close all;
clc;
xss=0.01;
wf=40;
wn=20;
zeta=0.1;
A=0.1; B=0.04;
wd=wn*sqrt(1-zeta^2);
t=0:0.005:4;
X=xss*cos(wf*t)+(A*sin(wd*t)+B*cos(wd*t)).*exp(-zeta*wn*t);
plot(t,X,'r','LineWidth',2)
grid on

envelope(X, 100, 'peak')