I see what you mean Betamax, i've looked on the web and there are sites that refer to 'i' as root of -1, but in my old tech college notes (going back a few years now) we used a lower case j. Don't understand it now though, you forget things if you *DONT* keep your skills up.
actually, the "j" was implimented for electronics since the letter "i" was already being used by current (how they got "i" to be current, is beyond me) but, both are acceptable forms of numbers that dont exist yet still have relevant uses
Does it really matter whether you use i or j? Either way, it's an imaginary number, so you're just designating some letter to take its place. It's not like j or i have a different value or anything (although I must admit, i's are written much faster). I personally used i, but I don't see why it should be any different from variables.