I am doing Signal and System home work..i need some help to confirm if my step were the correct method of doing it... here goes

*Determine whether the signals is periodic? and state its period.

Question 1 :

x(n) = u(n) - u(n-10)

Solution :

x(n) = u(n - T) - u(n - T - 10)

x(n) = u(n - kT) - u(n - lT - 10 )

since l/k cannot be express therefore the signal is not periodic.

Question 2 :

x(n) = sin (n)

Solution :

x(n + T) = sin (n + T)

T = 2 pie

= 2 x 3.142

= 6.238

T is not integer, therefore x(n) = sin (n) is not periodic signal