# Relation between time domain, DTFT domain and frequency domain

## Problem

The sampling frequency of a continuous-time signal is $S$ kHz, what does $\frac{\pi}{4}$ radians/sample in DTFT domain represent in Hz in frequency domain? Prove the relationship.

## Doubts

I am confused with DTFT domain and frequency domain and I do not how to put all these domains together.

There are $2 \pi$ radians per cycle.
So the puzzle now is to find the relationship between $\frac{samples}{second}$, $\frac{radians}{sample}$, $\frac{radians}{cycle}$, and your goal of $\frac{cycles}{second}$,