Why Use X and Y for Variables?

Date: 10/23/2002 at 01:14:17
From: Jennifer Connelly
Subject: Algebra

Why does everyone like to use the variables X and Y in an equation? I 
find other variables to be nicer. Please help me answer this question. 

Thank you.

Date: 10/23/2002 at 12:37:39
From: Doctor Peterson
Subject: Re: Algebra

Hi, Jennifer.

This page (listed at the bottom of the Dr. Math FAQ) gives a history 
of this usage:

   Earliest Uses of Symbols for Variables - Jeff Miller
   http://jeff560.tripod.com/variables.html 

As you'll see there, part of the answer is that x is not used as often 
as other letters (in French, in particular), so there were more of 
them available to early printers. But the only reason we can give with 
any certainty is that Descartes chose to take his knowns from the 
beginning of the alphabet and his unknowns from the end, and others 
followed his tradition. There's probably no more reason than that 
arbitrary choice.

If you have any further questions, feel free to write back.

- Doctor Peterson, The Math Forum
  http://mathforum.org/dr.math/