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From: ags@pucc-h (Dave Seaman)
Newsgroups: net.micro
Subject: Re: n-digit Pi algorithm
Message-ID: <2534@pucc-h>
Date: Tue, 24-Dec-85 13:53:22 EST
Article-I.D.: pucc-h.2534
Posted: Tue Dec 24 13:53:22 1985
Date-Received: Wed, 25-Dec-85 03:18:15 EST
References: <842@brl-tgr.ARPA>
Reply-To: ags@pucc-h.UUCP (Dave Seaman)
Organization: Purdue University Computing Center
Lines: 15

In article <842@brl-tgr.ARPA> SECRIST%OAK.SAINET.MFENET@lll-mfe.arpa writes:
>Does anybody out there know the algorithm for computing Pi to n-digits ?

A reasonably fast series for pi is given by

	pi/4 = 4 * arctan(1/5) - arctan(1/239)
where
	arctan x = x - x^3/3 + x^5/5 - x^7/7 + ...

so that

	pi/4 = 4 * [1/5 - 1/(3*5^3) + 1/(5*5^5) - 1/(7*5^7) + ...]
	       - [1/239 - 1/(3*239^3) + 1/(5*239^5) - 1/(7*239^7) + ...]
-- 
Dave Seaman	  					pur-ee!pucc-h!ags