i have a periodic signal $x[n] = \cos (\frac{2 \pi}{10}n)$.
I found this DTFT pair:
That's the only pair for a cosine function i found. But what is $\delta _{2\pi}$ ? Is it just a Dirac $\delta$ function for every period ?
And the $\pi$ before the brackets is just for a higher amplitude of the impulse ?