Why can one ignore the real part of a complex number because of Fourier transform "only using the rotational part"? Particularly, what property of Fourier transform is this?
Like given in this thread:
Essentially they say that (quoting clabacchio):
The reason why S=jω is chosen to evaluate AC signals is that it allows to convert the Laplace transform into Fourier transform.
The reason is that while S is a complex variable, what's used in the Fourier representation is just the rotational (imaginary) component, hence σ=0.