Talk:Positive number

ehr.. real positive number? what about immaginary positive numbers such as 3+3i?? smaffy

I don't think you call that positive. - Patrick 12:56 21 May 2003 (UTC)

what is it then?? smaffy

neither positive, nor negative, nor zero. - Patrick 13:18 21 May 2003 (UTC)

technically, its imaginary Pizza Puzzle

Technically, it is complex. Having both a real part (3) and an imaginary part (3i). -- Oliver P. 13:15 24 May 2003 (UTC)

Sure it's imaginary, it's just not purely imaginary. -- Toby Bartels 04:19 6 Jun 2003 (UTC)

Eh? Does this mean that it's also real, but not purely real? Oh, you've confused me now... -- Oliver P. 16:32 6 Jun 2003 (UTC)

No, it's certainly not real!

One terminology: Just as the rational numbers form a distinguished subset of the real numbers and the irrational numbers are simply all of the other ones, so the real numbers for a distinguished subset of the complex numbers and the imaginary numbers are simply all of the other ones (such as 3i and 3 + 3i, but not 3 or 0). Alternatively, every complex number may be written uniquely as a + ib for real numbers a and b, respectively the real and imaginary parts. If the imaginary part is 0, then the number is real; but if the imaginary part is nonzero, then the number is (at least in part) imaginary. Conversely, if the real part is 0, then the number is purely imaginary. This applies even if the number isn't imaginary either, that is if it's 0!

Another terminology: An imaginary number is any number of the form bi where b is real (such as 3i and 0, but not 3 or 3 + 3i). A complex number that happens not to be real is just, well, non-real.

Unambigous terms: purely imaginary and non-real.

-- Toby Bartels 02:47 12 Jun 2003 (UTC)

Thanks for the explanation, Toby. :) The terminology I was familiar with was the second one you describe, in which an imaginary number is a real number multiplied by i. It seems funny to use the terms imaginary and purely imaginary to mean different things! But I'll try to use the unambiguous terms from now on. :) -- Oliver P. 03:04 12 Jun 2003 (UTC)