Subject: RE: [MATHEDCC] square root of -1 history
From: Lindsey, Dr. Charles (clindsey@fgcu.edu)
Date: Mon Jan 24 2000 - 16:37:39 EST
I don't have a copy of the book, but Cardano in his Ars Magna states in
part: "you will have to imagine sqrt(-15)..." in his demonstration in
Chapter XXXVII (Witmer's translation). I don't know if this is the origin of
the term "imaginary" or not, but it is certainly suggestive.
Another source might be the web site maintained by Jeff Miller at
http://members.aol.com/jeff570/mathword.html
This site lists some of the earliest known uses of various mathematical
words. It's a good one to bookmark. I know it's a .com web page, but the
author seems reliable and has documented his work pretty well.
Chuck Lindsey, Ph.D. clindsey@fgcu.edu
Director of General Education
Associate Professor and Program Leader, Mathematics
Florida Gulf Coast University
10501 FGCU Blvd South
Fort Myers, FL 33965-6565
Phone: (941) 590-7168 FAX: (941) 590-7200
http://itech.fgcu.edu/faculty/clindsey
> -----Original Message-----
> From: Paul Hertzel [SMTP:hertzpau@niacc.cc.ia.us]
> Sent: Monday, January 24, 2000 2:07 PM
> To: Martha Haehl; mathedcc@archives.math.utk.edu
> Subject: Re: [MATHEDCC] square root of -1 history
>
>
> >1. Does anyone know what mathematicians first studied the square root of
> -1
> >and when it was first called an imaginary number?
> >
> >Martha
>
> >It was Euler who first used the letter i for sqrt(-1) in a memoir in
> 1777.
> >
> >Phil Mahler
>
> But the i does not stand for "imaginary", rather, the term came into use
> after
> the symbol was already employed. In fact, "impossible" may have preceded
> the word "imaginary"; see 'Impossible Numbers', by Ernest Nagel in
> "Studies
> in the History of Ideas", where there may be a discussion of some of this
> terminology.
>
> Or maybe Chuck Lindsey knows if "An Imaginary Tale: The story of the
> square
> root of -1" mentions who first weakened "impossible" to "imaginary".
> Maybe
> in 100 years"imaginary" will have given way to "improper" numbers.
>
> Paul Hertzel
> North Iowa Area Community College
> Mason City, IA
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