# Plot the signals y(t)=sin(8πt) and g(t)=sin(18πt). Then sample both with a sampling period of 1/13s. Sketch the discrete signals. What do you observe?

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Joshua12 on 20 Jul 2016
Answered: Azzi Abdelmalek on 20 Jul 2016
I was given this problem and so far, this is what I've done
t = [0:0.1:13]
y = sin(8*pi*t);
g = sin(18*pi*t)
plot(t,y,'color','r'); hold on;
plot(t,g,'color','b');
What I'm really confused on is the sampling period and sketching the discrete signals. Did I implement the sampling time correctly in t? Is there a way to create a discrete signal?
Thank you.

J. Webster on 20 Jul 2016
Edited: J. Webster on 20 Jul 2016
Since t is an array, and you want y and g to be arrays, you need to use the . notation for operations...
so for example, replace
18*pi*t
with
18.*pi.*t

Star Strider on 20 Jul 2016
The ‘1/13s’ I believe should be the step in your ‘t’ vector.
This is how I interpret the problem:
tlim = 1;
tc = linspace(0, tlim, 250);
t = [0:(1/13):tlim];
y = @(t) sin(8*pi*t);
g = @(t) sin(18*pi*t);
figure(1)
subplot(2,1,1)
plot(tc,y(tc),'-r', tc,g(tc),'-b');
grid
subplot(2,1,2)
plot(t,y(t),'-r', t,g(t),'-b');
grid
That’s an impressive illustration of the phenomenon the problem is asking you to observe. (I made ‘y’ and ‘g’ anonymous functions for convenience.)

Azzi Abdelmalek on 20 Jul 2016
Use stem function instead plot function