> In signal processing complex numbers are useful for more purely mathematical reasons. Yes, but as always you can ask yourself: is this merely a coincidence (

> In signal processing complex numbers are useful for more purely mathematical reasons. Yes, but as always you can ask yourself: is this merely a coincidence (if there is such a thing as one) or is this reflecting some deeper relation between nature and mathematics? After all, a "signal" is quite a general and abstract notion.