example

figure;
N=35;
n=[0:1:N]
y1=cos(2*pi*n/N+pi/4)
plot(y1)
hold on
y2=0.5*cos(4*pi*n/N)
plot(y2)
hold on
y3=0.25*cos(8*pi*n/N+pi/2)
plot(y3)
hold on
legend({'y1=cos(2*\pi*n/N+\pi/4)','y2=0.5*cos(4*\pi*n/N)','y3=0.25*cos(8*\pi*n/N+\pi/2)'},"location","southeast")
xlabel('Numer probki')
ylabel('Wartosc')
title('Sygnaly')