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From: mcewan@uiucdcs.UUCP
Newsgroups: net.math
Subject: Re: re does minus one equal one - (nf)
Message-ID: <2966@uiucdcs.UUCP>
Date: Fri, 23-Sep-83 22:27:01 EDT
Article-I.D.: uiucdcs.2966
Posted: Fri Sep 23 22:27:01 1983
Date-Received: Mon, 26-Sep-83 22:09:59 EDT
Lines: 29

#R:watmath:-577900:uiucdcs:28200017:000:1074
uiucdcs!mcewan    Sep 23 16:34:00 1983

/***** uiucdcs:net.math / watmath!ljdickey /  8:40 am  Sep 15, 1983 */

  
>  I also am not quite sure of what makes this go wrong, but I have observed
>  that the square root of 1 is also -1.  
  
You are getting close to the problem.  Yes, it is true that -1 is a number
that squares to 1, but just because of that you should not conclude that
the square root of 1 is -1.  The functions (square) and (sqrt)
are not inverses of each other.  

To illustrate this point, think about all of the solutions to the
equation            x**2 = 17.
If your training is like that of most, you would say that
x = +/- sqrt (17)   (plus or minus the square root of 17),
not just   x=sqrt(17).  
The point is that the idea of "plus or minus", is NOT built into
the function SQRT, the +/- idea is something that has to be expressed
separately.

The values of the square root function are non-negetive.
-- 
  Lee Dickey, University of Waterloo.  (ljdickey@watmath.UUCP)
                      ...!allegra!watmath!ljdickey
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