How can i plot three periods of a signal

Hello, i have the following signal and i want to plot three periods of it

t=[0:0.0002:20];

xc1=cos(2*pi*493.88*t);

How can i do it? Thank you for your help

Answer 1

[Image Analyst]

Try it this way:

% t=[0:0.0002:20];
% xc1=cos(2*pi*493.88*t);
% argument in cos = 2*pi*t/period.  So
period = 1/493.88
threePeriods = 3 * period
% Make 1000 points over that 3 period.
t = linspace(0, threePeriods, 1000);
% Make xc1 with that t:
xc1 = cos(2 * pi * t / period);
% Plot it
plot(t, xc1, 'b-', 'LineWidth', 2);
xlabel('t', 'FontSize', 15);
ylabel('xcl', 'FontSize', 15);
grid on;
caption = sprintf('Three Periods of cos(2 * pi * t / period), where period = %f', period);
title(caption, 'FontSize', 15);

[Deniz Bozdogan]

Thank you so much

Answer 2

[Scott MacKenzie]

If you want to plot three periods of a signal and do it by extracting the data from your existing code, then

t=[0:0.0002:20];
xc1=cos(2*pi*493.88*t);

idx3 = find(t>=3/493.88,1);
plot(xc1(1:idx3));