Matlab help

Show matlab scripts and plots for parts a,b, c

Thanks

num = [1];

den=[1 4 20];

sys=tf(num,den); % 1/(s^2 + 4s + 20)

step(sys) %very powerful and easy to use

pause

impulse(sys) % also powerful and easy to use

pause

t = 0:0.1:20; % vector of time samples

u = 3*sin(t); % the INPUT valuse

lsim(sys,u,t) %plot the response and the input

pause

y=lsim(sys,u,t);

plot(t,y);

3. Modify tf_demo.m to do the following: a) Use the tf() function to define a system variable for: x+++=4x6x8xft() Use the step() function to plot the response of the system for ft()=ut() (a unit step)