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Article #62

Re: Pencil & Paper Square root method

#62
From: Kelly Booth
Date: Fri, 25 Aug 1989 00:36
17 lines
1217 bytes
In article <491@watshine.waterloo.edu> pfratar@watshine.waterloo.edu (Paul Frattaroli - DCS) writes:
>                                              The root is the number of
>times you subtract + any decimal from the long division.

This algorithm requires OMEGA( root n ) steps to find the square root and
is analogous to division by successive subtraction (without shifts).

The earlier algorithm requires OMEGA( log n ) steps and is analogous to
the standard long division algorithm (subtraction with shifts).  It is
easy to derive this directly from the binomial theorem:

	Let sqrt(X) = 10a + b,

	then X = (10a + b)**2 = 100a**2 + 20ab + b**2

	The first division step finds a, then the iterative step finds
	b (note that 20ab is twice a in the tens place plus b).
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Message-ID: <11255@watcgl.waterloo.edu>
Path: arc1-ca.pugleaf.net!utzoo!utgpu!watmath!watcgl!ksbooth
References: <16075@watdragon.waterloo.edu> <491@watshine.waterloo.edu>

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Path: arc1-ca.pugleaf.net!utzoo!utgpu!watmath!watcgl!ksbooth
From: ksbooth@watcgl.waterloo.edu (Kelly Booth)
Newsgroups: uw.general
Subject: Re: Pencil & Paper Square root method
Message-ID: <11255@watcgl.waterloo.edu>
Date: 25 Aug 89 00:36:12 GMT
References: <16075@watdragon.waterloo.edu> <491@watshine.waterloo.edu>
Reply-To: ksbooth@watcgl.waterloo.edu (Kelly Booth)
Distribution: uw
Organization: U. of Waterloo, Ontario
Lines: 17