And as the spectrum of a discrete time sign, this identical spectrum will periodically repeat if we extended the frequency larger over and above $f_s$ such the spectrum proven is additionally precisely the same spectrum in just about every frequency band from $nf_s$ to $(n+1)f_s$ for just about any integer https://pginsector15gurugram.mystrikingly.com/blog/book-modern-pg-for-boys-in-gurgaon-osmstays/i/view_as_owner