[net.math] Re Using square roots in proofs

ljdickey@watmath.UUCP (09/13/83)

It is wrong to say that both 1 and -1 are square roots of 1.
Only one of them is a square root of 1, even though they
both square to 1.  
     Any decent modern calculus book will give you a good
example or two of this.  For instance, the widely used
text by Thomas, "Calculus and Analytic Gemoetry", 4th edition,
published by Addison-Wesley, on page 16 points out that
 
      the absolute value of x equals the square root
      of x squared.
 
Notice that this relies on the idea that the square root
be non-negative.

-- 
  Lee Dickey, University of Waterloo.  (ljdickey@watmath.UUCP)
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