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From: dje@5941ux.UUCP
Newsgroups: net.math
Subject: Re: does minus one equal one
Message-ID: <405@5941ux.UUCP>
Date: Wed, 14-Sep-83 08:51:17 EDT
Article-I.D.: 5941ux.405
Posted: Wed Sep 14 08:51:17 1983
Date-Received: Thu, 15-Sep-83 06:17:31 EDT
References: teklabs.2422
Lines: 15

There seems to be some confusion over the "1 = sqrt(1) = -1" reasoning.

sqrt(...) is a real-valued function that for each non-negative x maps it into
the unique non-negative y for which y*y = x.

Any equality of the form "sqrt(x) = y" can therefore make sense only if
y is non-negative!  sqrt(1) = 1, NOT -1.

Although we may say (loosely) that -1 is "a" square root of 1, the abuse of
language here does not extend to the use of the sqrt(...) function or to
any assertion of equality other than (-1)*(-1) = 1.

Dave Ellis / Bell Labs, Piscataway NJ
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