[net.math] does minus one equal one

stevens@teklabs.UUCP (09/12/83)

Two articles proved that -1=1.  One by Steve Summit went like

-1 = sqrt(1)

-1 = 1

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.  The other article said something
like sqrt(-1)*sqrt(-1) == -1.  This is true, but I think the conflict in
both cases could probably have been avoided if it was done in complex
numbers. i.e. let
			2*pi*i
		      e         = 1    
etc. etc.
-- 
Steve Silberberg

dje@5941ux.UUCP (09/14/83)

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
...!{hocda,ihnp4}!houxm!houxf!5941ux!dje
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