And because the spectrum of a discrete time sign, this exact spectrum will periodically repeat if we extended the frequency better past $f_s$ such which the spectrum proven can also be the exact same spectrum in each and every frequency band from $nf_s$ to $(n+1)f_s$ for virtually any integer $n$. https://pginsector15gurugram.art.blog/2025/07/28/book-modern-pg-for-boys-in-gurgaon-osmstays/