how to create this plot

plot for this sequence cos(pi/3n)+0.75cos(2pi/3n) in discrete time tnx

Answer 1

[Image Analyst]

I already did it in your duplicate question. Here it is again:

% Create data.
x = -3:11;
y1 = cos(x .* pi/3)+0.75*cos(2*x*pi/3);
y2 = [0,0,0,1,1,1,1,1,1,1,1,0,0,0,0]
y3 = y1 .* y2;

% Plot top graph.
subplot(3,1,1);
stem(x,y1, 'Color', 'k', 'MarkerFaceColor', 'k', 'LineWidth', 3);
xlim([-3,11]);
ylim([-2,2]);
grid on;
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);

% Plot top graph.
subplot(3,1,2);
stem(x,y2, 'Color', 'k', 'MarkerFaceColor', 'k', 'LineWidth', 3);
xlim([-3,11]);
ylim([0, 1.2]);
grid on;

% Plot top graph.
subplot(3,1,3);
stem(x,y3, 'Color', 'k', 'MarkerFaceColor', 'k', 'LineWidth', 3);
xlim([-3,11]);
ylim([-2, 2]);
grid on;

Answer 2

[Azzi Abdelmalek]

n=0:10
y=cos(pi./(3*n))+0.75*cos(2pi./(3*n)
stem(n,y)