History of the Radical Sign

Date: 04/17/97 at 10:26:17
From: Marc Younger
Subject: Radical sign

Who invented the radical sign?

Date: 04/17/97 at 14:10:37
From: Doctor Bombelli
Subject: Re: Radical sign

A wonderful source for this type of question is _A History of 
Mathematical Notation_ by Florian Cajori, from which the following is 
taken:

The word "radix" was used for square root in the thirteenth century or 
so, and was abbreviated as "R" or R with a slash though the right leg 
of the R, like the Rx symbol at pharmacies.

The symbol that looks like a check (radical sign without the "roof") 
originated in Germany, in the 1500's.  It started out looking quite 
like a musical note.  If you had a long expression under the radical 
sign, the expression was put in parentheses, and later, placed with a 
line over it. This is where the current symbol came from.  Descartes 
in his _La Geometrie_ (1637) seems to be the first to place the line 
on top for grouping.

So, no one really "invented" the sign - it developed over the years.  
But if you need a specific person, Descartes seems to be the one to 
first use the present day version of the symbol

-Doctor Bombelli,  The Math Forum
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