How can we find the fundamental period of this sinusoidal discrete function $x(n) = 10\cos{(\frac{4n\pi}{31}+\frac{\pi}{5}})$
I tried using the formulae $\frac{2π}{\omega}$ and got the answer 31/2, but since the function is discrete shouldn't the period be a whole number??
The function has period $31/2$ just as you answered it yourself. The period does not need to be an integer.