clear
f1=1000;
w1=2*pi*f1;
f2=234000;
w2=2*pi*f2;
taux=0.5;
t=0:1e-6:3e-3;
subplot(3,1,1)
plot(t,cos(w2*t));
hold on
plot(t,cos(w1*t),'r');
subplot(3,1,2)
plot(t,(1+taux*cos(w1*t)).*cos(w2*t));
subplot(3,1,3)
plot(t,cos(w2*t)+taux*cos((w2-w1)*t)/2+taux*cos((w1+w2)*t)/2);