I don't get why you use a for loop on i. It seems to me that the result you want is more like :
% constants similar to three plots
delta = 0.1; % F0/k deflection of mass under a force F0
% static deflection
omegan = 6; % natural frequency
x0 = 0.1; % initial displacement
dotx0 = 0.5; % initial velocity
t = (0:0.001:5); % time vector
i = 0; % counter for figure
for omega = [5, 6.1, 5.9]
x = x0*cos(omegan*t) + dotx0/omegan*sin(omegan*t) + delta*...
(cos(omega*t) - cos(omegan*t))/(1 - (omega/omegan)^2);
i = i+1; % increment the counter and so the figure to plot in
figure(i)
plot(t, x)
xlabel('time, t')
ylabel('displacement, x(t)')
title(sprintf('$$\\omega = %.3f$$',omega), 'interpreter', 'latex')
end
and just above is also a solution to your latex problem in the title.
and if this is what you wanted to do, a better way to code will be :
% constants similar to three plots
delta = 0.1; % F0/k deflection of mass under a force F0
% static deflection
omegan = 6; % natural frequency
x0 = 0.1; % initial displacement
dotx0 = 0.5; % initial velocity
t = (0:0.001:5); % time vector
omegavalues = [5, 6.1, 5.9];
for i = 1:length(omegavalues);
omega = omegavalues(i);
x = x0*cos(omegan*t) + dotx0/omegan*sin(omegan*t) + delta*...
(cos(omega*t) - cos(omegan*t))/(1 - (omega/omegan)^2);
figure(i)
plot(t, x)
xlabel('time, t')
ylabel('displacement, x(t)')
title(sprintf('$$\\omega = %.3f$$',omega), 'interpreter', 'latex')
end
