MATLAB: How to plot varying cos function

Question

I have to draw a function like below

I need a cos function when its is between pi and 2*pi, and 0 function when it is between 0 and pi. Also I am trying to plot it for several periods:

syms t
T=1/(n/60)
if pi<=5*pi*t<=2*pi
    Qt = 0.001*cos(5*pi*t)
if 0<5*pi*t<pi
    Qt=0
end
plot(t,Qt,[0, 5*T])

Could someone help me to fix this code, please

Answer 1

Try something like this

t = linspace(0, 4*pi, 200);
y = cos(t);
y(y<0) = 0;
plot(t, y)
xlim([0 4*pi]);
ylim([-1.5 1.5]);