% M-file names must start with an alphabetic character,
%   may contain any alphanumeric characters or underscores

clear;  % Clear variables and functions from memory.
clc;    % Clear command window.


% 1.9 (a)
t = 0:0.01:30;
x = cos(pi*t) + cos(4*pi*t/5);
plot(t, x, 'LineWidth', 1.5);
xlabel('Time (sec)');
ylabel('x(t)');
title('1.9 (a)');
