Plot the graph and if the signal is periodic, what is the fundamental?

[bernardoprepmare]

Homework Statement

I am solving a work of signs and systems and asked me to find in the equations below the graph and the fundamental period

And in question 2 asks to plot the graph of the signs and also the convolution.

Relevant Equations

a)
x(t) = u(t-3)+u(1-t)

b) x(t) = 10cos(100t)-2sen(100t)

c) x[n] = 1- e^j4pin/7 + e^ j2pin/5

d) x[n] = (1/2)^n u[n-3]

2)
a) x[n] = (1/3)^n u[-n-1]
h[n] = u[n-1]

b) x(t) = e^2t u(-t)
h(t) = u(t-3)

I do not know how to declare time t and unit steps.

The image of problems to get a better understanding as well.

 

[bernardoprepmare]

I can solve 1a and 1b, but I could not figure out if a function is periodic or not.
Both were like this ...

a)
t = (-10:0.01:10);
x1 = t>=3;
x2 = t<1;
xtot=x1+x2;
plot(t,xtot)
axis ([-10,10,0,1.2])

b)
t = (-0.5:0.001:0.5)';
x1 = 10*cos(100*t);
x2 = 2*sin(100*t);
xtot=x1-x2;
plot(t,xtot)
axis ([-0.5,0.5,-11,11])

 

[RPinPA]

Is the cosine function periodic? What is its period?

 

[bernardoprepmare]

Is the cosine function periodic? What is its period?

Yes, I completed question number 1.
The letter A is not periodic and B is!
Your approximate period by the graph that MatLab gave me is something around 0.7.