clc;
clear;
close all;

%% Parameters
f1 = 2000;
f2 = 4000;
f3 = 6000;

f3_rec = -3000

%% Time vectors
t=0:1e-6:1e-3;

%% Signals
x = 1+0.5*cos(2*pi*f1*t)+2*sin(2*pi*f2*t)+sin(2*pi*f3*t);
x1 = 1+0.5*cos(2*pi*f1*t)+2*sin(2*pi*f2*t)+sin(2*pi*f3_rec*t);
x2 = 1+0.5*cos(2*pi*f1*t)+2*sin(2*pi*f2*t)+sin(2*pi*f3*t);

%% Plot
figure
hold on

plot(t, x, 'b', 'LineWidth', 1.5)
plot(t, x1, 'r', 'LineWidth', 1.5)
plot(t, x2, '--g', 'LineWidth', 1.5)

grid on

xlabel('Time (ms)')
ylabel('x(t)')

legend('x(t)', 'x1(t)', 'x2(t)');