really silly nit: why 3+5j instead of 3+5i?

[Frank Miles]

In article <8flaj9$7bs$1 at slb0.atl.mindspring.net>,
Andrew Dalke <dalke at acm.org> wrote:
>andres at corrada.com wrote:
>>Physicists also use "i" and "I" for current and yet still use "i" for
>>imaginary numbers also. The use of "j" is unfortunate given that most
>>of the scientific/mathematical world uses "i".
>
>
>Just scanned through one of my E&M books.  Can't find "i" used for
>current.  Found "I", and dQ/dt.  Also found J used for volumn current
>density.  Lower case "i" is used for imaginary numbers and i^ (that's
>i-with-caret) for unit vector along the x axis.
>
>Can't ever recall using "i" for current.
>
>                    Andrew
>                    dalke at acm.org

When I took circuit analysis, 'i' was used for current in the time-domain,
'I' was used for current in the frequency domain (e.g. Fourier or Laplace
transform of 'i').  Yes, J is used for sheet or volume currents, but this
is comparatively unusual.  My guess is that engineers are the most
populous users of complex numbers (or were in the past), so had some sway
in getting 'j' accepted as the imaginary unit vector.

I dimly remember having a similar confusion on first encountering this use
of 'j' -- but it doesn't take that long to adjust if you use it reasonably
frequently.  It's usually pretty obvious from context, after all.

	-frank
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