Re: A little lesson for sqrt(144) year olds.
From: Androcles (androc1es_at_nospamblueyonder.co.uk)
Date: 06/30/04
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Date: Wed, 30 Jun 2004 17:12:48 GMT
"Jesper Pedersen" <jesper@befunk.com> wrote in message
news:cbu7sn$a4i$1@news.net.uni-c.dk...
| "Androcles" <androc1es@nospamblueyonder.co.uk> wrote in message
| news:CmnEc.6449$MV.69480542@news-text.cableinet.net...
| <snip>
| > Yes, very probably, but remember that
| > "3 = sqrt(9)
| > -3 = -sqrt(9)" -Dinky the Deranged.
| > "This way sqrt is ALWAYS positive."-Dinky the Deranged.
| > and
| > "IF x <= 0 THEN sqrt(x^2) = -x" - Dinky the Deranged
| > is not written in the form -3 = -sqrt(9). There is a missing minus sign
| > after the word "THEN".
| > Perhaps -x = -sqrt(x^2) is equivalent to sqrt(x^2) = -x
| > because x is on the other side of the '='?
| > Maybe we should ask Dinky.
| <snip more commented quotes>
|
| You need to understand the fundamental difference between solving x^2=2
for
| x
I think the solution is -1.4142135623730950488016887242097.
Let's see.
-1.4142135623730950488016887242097 *
-1.4142135623730950488016887242097 = 2.
Yep, I'm right.
and applying the function sqrt(2). the sqrt is DEFINED as being positive.
Is it?
if x = [-b +/- sqrt(b^2 - 4ac]/2a, is b always positive?
| Otherwise how would equalities such as sin(Pi/4) = sqrt(2)/2 make any
sense
| at all? Surely you wouldn't claim that sin is dual-valued?
That rather depends on whether you use (x, iy) or (x,y), doesn't it?
Androcles.
|
| / Jesper P
|
|
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