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Article #843Re: Does this product converge ???
From: Jim Roth
Date: Wed, 23 Dec 1992 11:26
Date: Wed, 23 Dec 1992 11:26
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In article <1992Dec22.192535.29669@news.eng.convex.com>, Dave Dodson <dodson@convex.COM> writes... >In article <1992Dec22.165148.20421@draper.com> storch@draper.com (Joel Storch) writes: >>To prove that Product(k=3,infinity, Cos(Pi/k)) converges, first rewrite it as >>Product(k=3,infinity,1-2 (Sin(Pi/2k))^2). This product will converge >>(absolutely) if the infinite series Sum(k=3,infinity,(Sin(Pi/2k))^2) >>converges. The Ratio Test fails here but Raabe's test shows that the series >>converges. >Even simpler: The sequence of partial products is non-negative and monotone- >decreasing. Therefore it has a greatest lower bound, which must be the limit. But is the limit greater than zero? Geometrically, this product arises from a nested sequence of inscribed circles and regular n-gons (convex of course), starting with a triangle. - Jim >Dave Dodson dodson@convex.COM >Convex Computer Corporation Richardson, Texas (214) 497-4234
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Newsgroups: sci.math.num-analysis Path: arc1-ca.pugleaf.net!sparky!uunet!haven.umd.edu!decuac!pa.dec.com!engage.pko.dec.com!nntpd.lkg.dec.com!ryn.mro4.dec.com!3d.enet.dec.com!roth From: roth@3d.enet.dec.com (Jim Roth) Subject: Re: Does this product converge ??? Message-ID: <1992Dec23.162848.20221@ryn.mro4.dec.com> Sender: news@ryn.mro4.dec.com (USENET News System) Organization: Digital Equipment Corporation Date: 23 DEC 92 11:26:20 Lines: 23